I am currently developing a single-page web application that is focused on functionality. It doesn't really have or need long paragraphs of text, and those that are there are loaded dynamically via javascript and AJAX. 

Normally search engine optimization tips revolve around getting the right word count percentages, etc. But what are the best practices for SEO when your application is heavily reliant on AJAX? A landing page with descriptive text is not an option - it's important that users can immediately start using the application, and it's rather obvious what it does once it's loaded. 

With meta tags fading in importance in modern search engines, is link-building the only solution or are there tricks to help search engines know what an AJAX-based web application is about?