Content, to a search engine, is text. The most important text is that visible to the user, and each page should have unique content.
Pick a topic for the page, and stick to it. If you are going to include lists of items, do so in a larger context of sentences and paragraphs, as you will see in this section. SEO will involve making sure your keywords are evenly distributed on the page but appearing early rather than being buried near the bottom of the page. Don't worry about getting it right the first time. Pages may be edited, and each edit is a change which tells the search engine the site is actively updated.
Search engines do not understand graphic images. Each image you use should be described in full within the context of the page, or at least in the alternate text which may accompany the image. Use of image captions (legends) is recommended.
Meta tags are not as important as they used to be. The page title (which appears in the top of most browsers) should reflect the subject matter of the page. This is also the title used on most search engine listings. Make sure that each page has a unique page title. The description meta tag will be used by the search engine for the teaser given in their search results. Including a description prevents the search engine from creating a teaser from your content which may not reflect the intent of the page. The keywords tag provides the search engine with a hint for what keywords to look for within the content. Make sure if you include this tag that every keyword is in fact on the page. Do not repeat words in this list. You will be penalized.