Sounds horrible but is true: a lot of stealing and copying. Eventually you kind of start to develop a knack for it and learn to create your own flavour. You also start to recognise the patterns you see everywhere and why they work.
I learn a lot of UI design by using what I make (going through entering data, pulling up screens, printing, etc. as if I were the end user) and seeing if it works, asking others who use it a lot what is easy and what is not, and comparing with interfaces on similar applications.
I've been thinking about taking a classes to improve my UX/UI skills since they are becoming more important. I think it would really round out my skill set. Anyone have recommendation on more formal way of learning good UI/UX design process?