About Face 3 is a good read, as is Tog on Interface, but this isn't a discipline you learn by reading; concentrate on your feelings, and then think about why you're having them.

We all experience delight and dismay when using software interfaces - teach yourself to recognise those moments, and then step back and critically analyse why you're having that response.

User experience/interface design is about the word they have in common: the user; a thinking, feeling human being. You're already one of those. Listen to your own responses, and let them shape your decisions to an appropriate degree. The only irreplaceable qualification for this line of work is empathy.