While building the pages on your site, be aware of your code-to-text ratio and be sure to create more content than code. There are a plethora of free online tools that you can use to evaluate the site when it is complete. These tools have their own algorithms for calculating code-to-text ratio, which will give you a variety of results depending on which you use. That being said, the best rule of thumb is to keep your code simple and clean.
While you should always be aware of code-to-text ratio, cramming large amounts of text on a page is not necessarily the best tactic to improve SEO. Some search engines do not include it in their algorithm, and human audiences, as well as search engines, tend to stop reading large blocks of text after the first three or four paragraphs. You might achieve more success by breaking down long passages of text into sub-pages, each one optimized for its topic.