Roger Johansson adds to Garret Dimon’s tips for a better markup. The total package can work as a reference material for anyone trying to work on markup. Like, a lot of times, I end up creating with classitis but gets cleaned up on careful inspection. These guidelines can help right through your process of writing the markup.
One additional tip that has helped me is to create a semantic markup. Of course, its benefits are not unknown, however I find it useful for even communication between project members. The markup can be effectively used to convey content priority, design and the semantics. I have found this more efficient than any other form of documentation. Especially when someone else is going to do the styles. The markup can really build a project language.
Good markup can help you build accessibility inherently into the site, and maintaining it. Great tips there. Make sure you do not miss it if you hover anywhere around the markup.