When we choose an opening lead it is not an art but a science. Even the best thought out leads will sometimes work out badly for us. However, when it comes to leads against slams we have a few guidelines to help us along the way.
Against a No Trump slam, we should lead passively ( lead from what we do not have) .
Against a suit slam , we should try to be aggressive ( lead away from a King if we have an outside Ace, in anticipation of finding partner with a Queen to set up a fast trick).
Timing is everything before they get discards, so the race is on!