Hands have always haunted me. I have however come across several tips that helped me improve big time!
The best reference for hands is your own. Do different poses with your hand, and try to break it down. As for the process of breaking it down, there are various methods. I have attached an example of how I did one.
As for tips about the hand, there are many resources out there. Proko has several extremely in depth videos on the hand. You can also find photos of different hand poses with a simple google search.