How would you make your software easier to use?

1. What is the product supposed to do? A corollary is to ask, what can a user do with my product that he can't do without it? The answer to these questions should be a single, simple, focused answer.

2. What is the absolute minimum feature set we must have in order for the product to do what the user needs? Question EVERYTHING. If you're designing an email product, ask yourself if you even need folders. If you're designing a MS Word killer, ask yourself if you even need a Save. If you're designing a media player, ask yourself if even need a play/pause button.

After you have the minimum feature set, release the software and iterate quickly based on user feedback. Nothing can replace raw feedback from strangers who don't give a crap about you or your product. See what the users like and dislike about the product, based on first hand observation.

More tricky is keeping the product simple in response to user feature demands. Adding features is good, but only when you do it in such a way that it complements your answer to the original question: "What is the product supposed to do?"

You have to think about how each and every additional feature deeply integrates into your existing product, rather than tacking features on haphazardly. This is difficult to do. Google does this especially well (Search, Gmail).