Tips for drawing hands:
-Fingers do NOT all end in a straight line across, the middle finger is usually the longest followed by the ring then first then pinky and finally, the thumb.
-When drawing a palm, you must remember that it isn't flat, there are creases and bumps. Take for instance the bump on the palm made by the thumb, that is the main one.
-Wrists are not just staight, they have an area that comes in slightly from the palm of the hand that extends into the arm.
-Fingers have different sections and aren't just lines, they have bends, and not only two, but three!
-The length of the palm is actually the same as the length of the fingers.
My main suggestion though, is to look at your hand (like STUDY it) and just draw what you see from different positions. It is probably one of the best ways to learn.