Recent Google updates specifically target thin (low quality) content. It's very important that your website is built in such a way that the user experience is intuitive. Text that is stuffed with keywords, an unusual page of just "helpful links", over-optimization - these things do not contribute to the user experience and can actually hurt your search engine rankings.
- Headings - aim to include important keywords in Headings (h1, h2, etc.) so that your pages have clear structure and hierarchy, as well as letting users know right off the bat what they can expect to gain from this page of your website.
- Body Copy - there have been studies supporting the idea that top-ranking web pages should have at least 2,000 words of text. While it's true that more content means more keywords for search engines to detect, remember that the user experience trumps any arbitrary word counts. If your message can fully and accurately be delivered in 100 words, then don't write 2,000. Website copy should sound natural, not stuffed with keywords, and be well-edited.
- Alt Text - Alternative Text is a metadata attribute that describes the content of an image on the web. You can think of it as giving your image a title or a caption. Alt text is primarily used for accessibility purposes to help visually impaired users understand all of your content, but also is used by search engines to interpret images. Include keywords in alt text when you can, but remember that it still has to be a coherent statement that will make sense to users with accessibility needs.
- Internal Links - Well executed internal linking can eliminate the need for trying to write too much text or trying to deliver all of your information on one web page. Internal link structure should help users jump back and forth between like pages, back to category pages, etc.