With the new structure and power of the Drupal 7 theming engine I would have to say that there has never been a better time to be a designer for Drupal. As a designer, I would argue not to throw everything and the kitchen sink into a new theme. Start small and finish big. 

When I start with a new design I sit down at the kitchen table or at my desk with a pencil and a blank sheet of paper. This process can go on until I have sketched out every possible permutation for a design, because I don't want to have to stop when I'm in Illustrator, or Photoshop to rethink an element I hadn't considered. The inspiration phase can be enriching, but the development phase can be frustrating. So with your sketches in hand sit down and design to your hearts content. After all you're a designer and that is what designers do.

From Flat File to Full Site

Taking a flat image file and turning it into a full site is probably the best part about designing websites, at least in my opinion. Though to start any site it is all about the rebar, and for every site I have developed in the past year I have used the 960 grid, developed by Nathan Smith (http://960.gs/). Other designers have their own methods, and creations, but I have found the 960 Grid framework to provide the most flexibility.

Next, consider building the site in HTML, and I do mean HTML. Don't go about trying to code in your hooks and calls in PHP just yet. This way you can work out all the styling issues more easily, and know where the problems are coming from. Especially if everything is working in your plain HTML, and something breaks in your PHP code you'll know where to start looking. A solid framework with a solid stylesheet allows for a robust site.

Frameworks

Ideally not every site you design or develop in Drupal will fall into a framework, and many designers agree that frameworks can at times hinder a design. I don't generally believe that frameworks are evil or that you shouldn't use them. I fall into the camp that looks first if a framework is necessary for your site, or if a custom structure is needed. Never fit a mold if you don't have to, and don't be afraid to break the mold when you need to.

That said, here are two other frameworks to consider when developing your next theme:

1. Blueprint CSS
2. Less Framework 4

The development cycle of a theme is much like this blog post, never complete. In every theme there is something to be learned, and something to be changed.

Taxonomy: Planet DrupalDrupalDesign