When incorporating different languages into a site, a business should start with a carefully mapped information architecture. You need to know how the different language pages will be incorporated and where they will exist on your site or sites. Consider what domain will be used for each language and how that will be structured. You can use Domain Directories, ccTLDs or separate sub domains to manage this infrastructure. Domain directories are typically the simplest option as they then work as one SEO campaign. However, then the domain is typically using one server location so bandwidth considerations should be taken into account.
Once the structure of your site is mapped out and set up, you will need to consider how you will translate your content into the languages you wish to include. There are many free and paid translation applications available on the web, one of the most popular being Google translate. While these low cost or free options may seem appealing, it is highly recommended that you utilize a professional translator to translate your content. Automated translation tools often leave content filled with awkward phrases and grammatical errors. Also, if you are not particularly familiar with a language, it will be difficult for you to ascertain whether you are using the right keyphrases. A professional agency can help to ensure your target keyphrases are appropriately used in clean content.
You may need to tackle translations in a phased approach, but including SEO in multiple languages will help with your global web presence.