The most important principle I can think of is to make sure that every major UI element corresponds to a user's desired end result. If I truly care how something is done, then I have no problem going to the advanced options. Otherwise, I probably want a big button that just gets me to the result, in whatever way it thinks is best, while I go make a sandwich.

Along those lines, any required interaction on my part should all be at the beginning whenever possible. I don't want to come back from making my sandwich and find that the program has been idle for several minutes because I wasn't there to click "Next".