Google shared best practices for websites that allow users to create their own websites or host users’ data, like Blogger or Google Sites. This class of websites is often referred to as freehosts, although these recommendations apply to certain “non-free” providers as well.
- Make sure your users can verify their website in website management suites such as Google’s Webmaster Tools.
- Choose a unique directory or hostname for each user.
- Set useful and descriptive page titles.
- Allow the addition of tags to a page.
- Allow your users to use third-party analytics packages such as Google Analytics.
- Help your users move around.
- Help search engines find the good content from your users.
Read the entire post on Official Google Webmaster Central Blog.