Guillaume on SEOmoz has written a interesting post on 24 On-site SEO Checkups For Clueless Developers/Marketers.

The list of SEO on-site tips touches up the basics. However, Guillaume has rightly said that manty SEO consultants and web developers forget these basics at the time of launching a site. The twenty four tips will for sure ensure that any link building or link baiting effort gives maximum results.

Some of the tips are:

1. Run a $100 Adwords test campaign after your initial keyword research, helping you do the best themed/relevant keywords on-site optimisation.
2. Ensure there is a well written, non-duplicated attractive Title / Description tags on every page.
3. Verify that almost every single piece of relevant content on your site is somehow static to the page it was written for and is not a text image (double check that with a text browser).
4. Revise the On-page content to be sure there is a minimum presence of your themed keywords on every page. Don't try to go overboard, just think as if you'd be the user.
5. Double check your code to make sure you've got your content titles and subtitles under H1 / H2 tags.

Take a look at the complete list.