Headset press tools fit headsets. Nice method, and really healpful topic. -Usually what I do. If you want to do it properly, and not risk flaring the headtube by having the cups come out at dodgy angles, then buy one of these: Basically, you insert that into the headset so it expands out inside the headtube, then bash the top with a mallet. Saves having to bash, move screwdriver/whatever round, bash, move..etc.