With hands, draw the hand you don't draw with (man, this sentence sounds confusing). Make it take lots of various poses, and draw it, over and over and over again. Try and think in volume, not in outlines. For instance try drawing circles or elipses for each phalange, or draw a basic stick skeleton before drawing the outside.
Same kind of think for faces, start with the basic structure. First a circle for the whole thing, then a line for where the eyes will go, one for the nose and the mouth. Don't only draw faces facing you, draw all sorts of angles and points of views. Draw the whole thing to have an idea of how the features relate to each other, then draw specifics too, such as just a mouth with nothing around it, just an eye, etc.
Use real-life models first, for instance pictures, people if you can get to pose for you. Once you feel you have some concept of that, look at different artstyle and what they're trying to do. Look at artstyles you don't want to have too, they're still interesting. Try and imitate them just to see what they're like. But in the end try to build your own. What's a nose as drawn by you? An eye? A mouth? A hand? You'll have to answer these questions. Experiences artists usually have a recognisable style, you'll have to find yours, and you'll have to be happy with it, because it might not be what you wanted it to be. To some extent, your style isn't something you have complete control over.
Good luck!