Search marketing accounts for the largest share of online ad spending by a long shot. eMarketer predicts that it will continue to dominate in coming years.

As a result, it is important to understand how your business can benefit from search marketing. The vast majority of online searches are in languages other than English; therefore, it’s important to understand how to approach search campaigns when dealing with international markets.

We spoke with 10 search experts about how marketers can improve their international search engine marketing (SEM) strategies. We’ve outlined the top 13 tips here. Join the conversation by adding your international SEM tips in the comments below.

1. Go Local with Keyword Research

Machine translation is not an option when it comes to creating international keyword lists. Independent SEO Strategist Joost de Valk says, “Talk to native people or preferably native search marketers and get the real keywords for your business in that country. Far too often do I encounter people blatantly translating keywords from one language to another, thinking that a translation agency will know what it’s doing. They don’t. You need someone who has grown up in the country you’re targeting, speaking its language.”

“If you can hire a local SEM firm or at least [one] on the same continent, you’ll have the advantage of language support, understanding of culture, etc.,” says Adrian Salamunovic, co-founder of art company DNA11, which sells its product in more than 50 countries. “Keyword research and proper ad copy often come down to well-written copy and understanding of ‘soft factors,’ such as nuances in language and culture.”

Christian Arno, founder and managing director of UK translation company Lingo24, suggests to conduct separate research campaigns for countries that share a language. “You will find differences in the way Germans and Austrians, or Mexicans and Argentinians, search,” he explains. “These are often cultural, and peculiar to searching habits, in addition to known linguistic differences.”

Furthermore, Arno notes that “there are often several ways of translating — or indeed localizing — a key phrase.” Accordingly, he recommends that marketers create broad keyword lists. “Instruct your foreign language Internet marketers to give you all the options they think might work in your local market. Then test, test, test and let your analytics data decide. It’s often not a translator’s favorite rendition which works best in the long run, and if you can generate ROI from a broader basket of search terms than your competitors, so much the better.”

2. Do Test English

Running international search campaigns doesn’t mean excluding English completely.

“In some foreign language markets — generally those where English is commonly spoken — it can be worthwhile running campaigns in English as well as the native language,” says Arno. “Make sure to run them separately as the English which works in one locale may be different to others.”

3. Look Out for Language Mash-ups

“Sometimes English terms make it into another language and supplant the ‘correct’ original native use of a particular phrase,” says Arno. “For example, in Italy, a top search phrase for travel sites is ‘voli [flights] low cost’ rather than ‘voli a basso prezzo’ as you’d expect. This phenomenon should come out in your keyword research, but you might want to give it as an example to your foreign language Internet marketers to make sure they know you’re onto it.”

4. Capitalize on Local Holidays

Explore additional opportunities during local holidays,” says Ting Ting Wang Jager, senior manager of paid media at search marketing firm Covario. “Because April is traditionally when students start the school year and new recruits enter the labor force in Japan, a smart SEM practitioner would weave this renew/refresh message into existing ad copy.”

5. Advertise on Local Search Engines and Social Sites

Baidu has a 75.8% share of China’s search engine market. Google is a distant second with a 19.2% share.

“Google rules, but not everywhere,” says Bas van den Beld, search and social strategist and founder of blog State of Search. “There are a few countries in which Google gets beaten by local search engines. Think of Seznam in the Czech Republic and Yandex in Russia. Keep these local search engines in mind; it might give you more traffic and more conversion in those countries.”

“Facebook and local social networks also are important places to advertise,” says van den Beld. “Same goes for advertising on YouTube. Check who watches a lot of video (I know the Dutch do) and target those. Not just on YouTube, but also in SERPs [search engine results pages] which have universal [search] results with videos. So, check the SERPs to see where your ad can stand out.”

When it comes to social networks, look outside of the top English-focused social sites for local insights as well. You may find that local sites are even more highly trafficked than the mainstays that seem ever so pervasive in the United States and UK. “YouTube, Facebook and Twitter are blocked in China,” says Wang Jager, “However, you can still generate and capture buzz in this largest Internet-using country by utilizing RenRen, Tudou, Youku and Sina Weibo.”

Liz Elting, co-founder and co-CEO of translation company TransPerfect, cautions against assuming that international search engines and social sites work similarly to your local counterparts. “No two search engines use the exact same algorithm.” she says. “The optimization techniques required for the Chinese search engine Baidu, for example, may be vastly different from those needed to optimize for Google. Businesses that want to reach targeted users need expertise not only in language, but also in culture and technology.”

6. Make Every Character Count

“Most search engines limit the number of characters you can use on each line of your PPC ad,” says Elting. “Unfortunately, if you try to translate an English ad, the resulting translation will likely exceed the limitations imposed by the search engine because the number of words and length of the words are often longer in other languages. Therefore, it is important that the adapted ad is edited to fit within the character length limitations, without sacrificing the message you are trying to communicate.”

7. Don’t Compete Against Your Local Team

“Make sure you are not ‘doubling up’ with the local country marketing team, says Lisa Myers, CEO of SEO agency Verve Search. “I’ve seen numerous occasions where a company is bidding against themselves. For example, an agency is hired to do the SEM internationally but then the local offices in each country are still doing their ‘own’ campaigns. This is obviously a waste of time and money. But don’t discourage the local marketing teams — they are a huge asset. After all, they speak the language.”

8. Don’t Overbid on Keywords

“In other languages, there’s often less competition doing international search,” says Ben Kirshner, CEO of search engine marketing agency Elite SEM. “You don’t need to bid the same amount as you would in the U.S. and as a result, you can save a substantial amount of money for your client by bidding less on different inventory.”

“There are a number of competitive research tools that are free and can point marketers in the right direction when determining bids for international SEM campaigns,” Kirshner explains. “For example, Google Keyword Tool offers real data on traffic estimates and helps expand your keywords (as long as you have a Google AdWords account). Another tool that I like to keep under my international SEM belt is Google Traffic Estimator. This goes one step further from Google Keyword Tool and suggests CPC (cost-per-click) rates, local monthly searches and more.”

Kirshner continues, “One of the most insightful bidding tools out there, in my opinion, is Google Global Market Finder. Using this tool, marketers can type in a keyword like ‘hard drive’ and select a territory or region such as South Korea. What you get back is a geographical distribution of locations that have enough volume estimates associated with that keyword and suggested bids based on this data.”

“Not to sound old-fashioned,” Kirshner says, “but there’s also a non-techie resource that is just as (if not more) helpful in setting your bid prices: Google reps. They can pull Query Visualization Reports, which will identify similar keywords and their bid prices in the U.S. versus how they are performing in other countries like South Korea, Portugal and India. The added value component of these reports comes in the form of competitive analysis on what other competitors are bidding on and whether their bids are increasing or decreasing.”

Kirshner also suggests checking out more in-depth tools that, of course, come at a cost: SEM Rush, Ad Guru, SpyFu and Compete are subscription-based models that help marketers set their bid rates.

9. Use SEO Techniques to Research Competitor SEM Strategies

Any search marketing campaign should be enriched by a healthy amount of competitive research. Myers believes that researching for international campaigns may be even more important though, as competitors may have already done local research and testing from which your business can benefit. She explains:

“You can learn a lot from what your competitors are doing and, although you can’t really know what keywords they are bidding for in their paid search campaigns, you can find out what keywords they target for organic/natural search by having a quick look at their title attributes and page content. The keywords that they target organically will often be the keywords that generate the most traffic as well.”

10. Define Your Success Criteria

“In order to determine whether or not a campaign is successful, you must define your goals,” says Elting. “Are you trying to lower your cost per action? Are you trying to lower your cost per click? How are you defining a conversion? Do you want more people to submit a quote request? Make sure you have defined goals in advance of your campaign to prove that what you are doing is valuable.”

11. Make Conversion Easy on the Landing Page

“If your goals have anything to do with a conversion (and they should), then you need to do everything in your power to make a conversion easy for your visitors,” says Elting. “On the landing page, you should give the customer the opportunity to register, get a quote, contact you or make a purchase. The easier you can make it for a visitor to convert, the greater the likelihood that you will have success with your international search engine marketing campaigns.”

Furthermore, Myers insists, “Don’t fall in the trap of cutting corners and using the ‘one size fits all’ sentiment when it comes to landing pages. The temptation to use the .com domain for all countries just because they understand English is not good enough, at least not if you want conversions. Invest in translators or, even better, use search professionals in the relevant country you are targeting to create landing pages for your paid search traffic.”

Alyssa Paris, marketing manager for international translation and localization company Acclaro, provided more food for thought regarding landing pages: “Localize your landing pages with the target culture in mind, taking into account different payment options, legal restrictions and communication conventions.”

Salamunovic says “If you can’t afford translation services or full-blown translated sites, the next best thing is geo-landing pages — for inspiration, take a look at how LivingSocial customizes their offer pages (visually) for each city.”

12. Test, Test, Test

“For SEM, the same thing holds true in North America as anywhere else,” says Kyle Peterson, senior global account manager for PR and marketing firm Clement Communications. “You can’t write one ad and hope it sticks. You need to be testing and writing copy on a continuous basis to find out which headlines, words, calls-to-action, etc. resonate better with the audience in your newly targeted country. Again, it goes back to language: a native speaker is necessary to effectively test different writing styles.”

Think local when choosing analytics tools, suggests Paris: “Select the appropriate market-specific analytics tool to track your progress. Don’t compare results across countries, but rather, analyze your relative progress within each locale.”

Kirshner suggests asking your translation agency to make you a translation guide, or “cheat sheet,” so that you understand what you’re looking at in terms of ad groups and can optimize keywords that aren’t performing well.

13. Crowdsource Keywords

“Make sure you’re asking your users and other in-country contacts for more terms,” says Arno. “Use feedback forms to ask users how they think their friends would search for your product or service. We use our own survey form when clients have used our service to ask this, among other questions, and advise clients to do so. Often you only see these forms if you’ve actually used a service.”

We asked Arno if he had seen any dramatic improvements from using crowdsourced keywords. He explained, “We get the odd phrase, which proves useful over time. It doesn’t transform our business, but like lots of the other steps we take, it incrementally adds to it — and all the little things add up!”

The Future of Search Series is supported by SES San Francisco Conference & Expo. Join more than 6,000 marketers August 15-19 at the Moscone Center for five days of education, inspiration and conversations with the most important voices online. Learn about the industry’s most pressing developments — everything from Google Panda to YouTube LIVE — and every essential topic, including email, display, mobile, search, social media, video and more. Register with “MASH20″ to save 20%. Join the discussion: #SESSF.

More Search Resources from Mashable:

- HOW TO: Optimize Text Ads for Search
- Why Your Business Must Embrace the Foreign Language Internet
- 5 Tips for Marketing Online to an International Audience
- 5 Tips for Developing a Global-Friendly Website
- 5 Ways to Improve Your International SEO Strategy

Image courtesy of iStockphoto, pailoolom, skodonnell, fally

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