10 Lessons on Game Usability
Business Week has a great piece look at some basic fundamentals of game usability. They list 10 lessons which game designers need to know and should follow in their games. You can read the article here.
I think this is a fairly good list and is definitely something to keep in mind when designing your games. I can remember lots of times even I have just quit playing a game because of various usability problems where I otherwise probably would have continued playing.
