The most important part of SEO is making sure your site has unique and fresh content. If the content on your site does not appear elsewhere on the web, the search engines will weigh it more highly than copied content. On the same token, newer content is weighted more highly than aging content.
Don't overemphasize SEO as part of your business. SEO is important, but it's more important to produce a quality product, provide excellent customer service, and fill your website with useful, timely content. If you do all of these things well, and pay just the slightest amount of attention to SEO, you'll find your business doing well.
Make sure the text surrounding an image really matches the content of the image. The text will actually affect the ranking of an image on a page, so if they have nothing to do with each other, your image could pop up in search engine results that you don't want it to show up in.