I was always taught to design on paper first... (Thanks Jo). I think it can often be quite obvious when some one has gone straight to a computer without first drawing out their ideas the old fashioned way.
Using a pencil to explore initial ideas is so much easier and quicker than on a computer; you tend to not to get bogged down by little details, and instead, flow far more freely. I find that I temporarily forget about the restraints of a computer; whether it be traditional margins and columns, or the stumbling block of how to create a certain form in illustrator.
It's just great to step away from the screen sometimes, if only to give your poor burnt retinas a break. I also think it goes some way in helping tackle that horrible 'creative block' we all encounter from time to time.
Here's some examples of a project I've worked on recently, showing how sketches go from paper to screen.
So, next time you're working on a project, why not try ditching the mouse for a while in favour of a pencil?