Find a good hand position!
Just like when drawing with pencils on a paper you need to be able to freely move your hand without convulsing any part of your body and especially your arm. Even when you got a comfortable position for a pencil, work on the position with the tablet because the stylus is different from your other pens.
Also the surface is differently thus the tactile feedback is too. This leads to a different feeling of control over the lines. But there only making a mess of colors and brushes like Wolfpaint suggested.
Draw fast and learn to use stabilizers.
A fast swing over the tablet usually gets your really smooth and dynamic lines. Drawing slow usually creates little bumps in the lines. This is also the case on paper but it's far worse with any tablet I've drawn on.
Stabilizers try to smooth out/correct your lines while your drawing. This seem like cheating a bit at first, but it really helps so much. Many programs contain them with a controllable amount of stabilization, so you need to find out how much correction you want for wich step.
I personnally use something like 20% for outlines and very little to nothing while sketching but that's different for every digital artist I know.
Good luck :)
