I often develop user interfaces for my company, and I always ask myself "Is this useful and intuative enough?". I always try to boil down a few patterns in a particular product as possible.
What are your general guidelines to develop interfaces?
Steal from everywhere! Look at the best examples of UI near what you're trying to do and "borrow liberally". What works? What doesn't? You're a user, too -- what tools do you like and dislike for their UI, and why?
I find this works best when you "borrow" from multiple different great UIs and combine the best lessons from each.