An efficient offensive tactic is to monitor which cards are still in play and which have been discarded. You can determine your opponents' possible hands by observing their movements and modifrummy bossying your own approach accordingly. For example, you may decide to keep cards that could finish their set if you see that your opponent is gathering a particular suit or number, which would keep them from winning. The ability to concentrate on drawing cards that will help you finish your hand rather than just discarding can also be a big benefit of forming melds early in the game.