Butlerford45 has got it right. Basically, you load as much powder into the case as it will hold and be compressed slightly when you seat the bullet. About 1/16 to 1/8 an inch is enough compression. Some folks put a cardboard disk or "wad" between the bullet and the powder, some don't. Some add a "cookie" or disk of appropiate blackpowder lube between the wad and the bullet as the wax based lube on the bullet dosn't work well with black powder. This last is especially useful in long guns. Mike Ventuino has a couple of books on the subject. 
Holiday
Holiday
