I often get asked for advice about picking a Drupal theme. Themes are extensions of the Drupal content management system which allow a site admin to quickly change the look and feel of their site. You just download the theme you like, install it, select it, and your whole site has a new design.
However, like finding high quality Drupal modules there are some good rules of thumb to follow in your theme search.
Strategy 1: Find A Drupal Theme Close to What you Want
This is the simplest solution. I like to review the screenshots on the Drupal Themes page. Some themes don't have screenshots, but those are often lower quality anyway. If you see a theme that sounds good or looks good, the next stop is to head over to the Drupal Theme Garden which has live demos of all the themes. You can test things out without installing them. This is also a great place to browse the themes.
Often, though, a theme that looks close will quickly fall apart on installation and fixing it can take more work than modifying a solid base theme. So, if you find that your "close enough" theme is falling apart, you might need to take a new strategy.
Strategy 2: Modify a Solid Base Theme
Zen and Bluebreeze are a great base theme. Change a few images, a few colors, a few css properties and you can be all set. For the more "old school" folks who like table-based designs the previous standard was the Box Grey theme.
Ok, but what if you have a great design, you don't want to fight with anyone else's styles you just want to build up your theme.
Strategy 3: The Solid Foundation
So, you're already a designer and you are comfortable with CSS and you want a blank slate to start from. Great - use the Hunchbaque theme by Al Steffen (aka zarabadoo). This is a solid base theme, but is just black on white to begin with.
Strategy 4: Build it from the Ground Up
Check out the theme developer's guide in the handbook. From there you can build very precisely whatever you want.
Other tips? What other themes do other people like? What are your strategies for building themes?