There’s lots of information available on WordPress’s codex about how to create themes for your blog, all of it dealing with the filters and actions you can use to manipulate the active content on your blog in cool ways. It goes without saying that those are important pieces of information, and in fact there are some outstanding tutorials for putting together a theme that you should definitely check out. WPBits is one such resource.
But I’d like to talk about some concepts that happen before you get to the active content: the HTML, and how you go about designing a theme which has to exist in all those varying pieces yet all go together to create one cohesive whole. This is a very high-level tutorial, meaning that specific details will be omitted in order to introduce the most basic concepts. I’m writing more about the workflow than about the process, if you follow me!