Putting the Cart Before the Horse

First off, Im sure that for every experienced Drupal developer, they have developed thier own method to the madness of setting up a site. I also figure that the order may differ depending on the overall site type that is being built (social network, ecommerce store, etc...). Still I noticed ways in which I was placing the cart before the horse through my own inexperienced use.

Basically (and some of you know me from the last Drupal meeting) I'm attempting to create a site that is very much informational but that will contain ecommerce features as well. It will have a mailing list and it will have listings of distributors, vendors and other contact info. Some fields I will need to hide from guests, authenticated users and any other users that have a role other than administrator, moderator, or contractor.

One thing I did manage to do is avoid working on the theme first. Im a designer so naturally I would gravitate towards getting the site to have a particular color scheme and CSS sheet. Once I got to figuring out layout, I realized that I might need to think a bit more about how the site will function, causing me to look into the module. Eventually I added Ubercart without really needing to focus on the catalog portion right that second. "You gotta crawl before you can walk."

Any advice re: order of operations? I would be curious to know the ideas you have and constructive criticism of my "method of madness".