So, anyone else have a group full of these? My groups (i currently roleplay on Tuesdays, Thursdays and Saturdays, and play Warhammer on Monday. Busy stuff.) all usually carefully place dice facing up the way towards the result they want. So, in gurps, there is a pile of D6's next to each player showing 1's. In 7th Sea, a pile (a big pile) of D10's showing 10's.
Another one is to roll all your dice, choosing those that roll the desired result to be your primary dice. Additional dice showing 1's or 10's or whatever are placed into a secondary dice pool.
If dice show poor results a lot, it is felt that you should change the dice to other, luckier, dice.
You should not allow dice to be contaminated with a system that prefers other results. In other words, don't use a Warhammer (6's prefered) in a game of GURPs (1's prefered) as the dice will get confused and shall give you bad luck.
For players with time on their hands, it is common to stack dice within their dice cubes all facing the desired result upwards. The interesting question is, 'which way is up?'