Jokes are extremely important when it comes to the game of Rummikub. No other tile has the strategic possibilities that a joker has, so it is wise to learn how to use it. Since the jokers represent any tile in the deck, they are obviously the easiest to use, and the most versatile. However, they are also the most versatile to your opponents whether or not they have any in their rack. They can be used both offensively and defensively and it is important to be aware of which way you want to use them.
The first thing you want to look at is how many players are in your game. The more people you have on the table, the more chances it can be reused. You need to remember that anyone may replace the joker with the tile it represents and then reuse it in another meld. This includes you as well as your opponent. If you are playing against only one other player, you both have the same number of turns and therefore the same number of chances to reuse the joker. The basic strategy with the joker is to improve your chances of use and reuse and to limit the chances of your opponent.
The easiest strategy, defensively, is to attempt to play a joker so that it cannot be reused, or to play it to minimize the chances of replacing it. With three or four players, this is particularly to your advantage. The best defensive play in the early part of a hand is to play the joker as an Ace or a 13 in a run, making it replaceable by only two tiles. You are positioning it as well so that no other tiles can be laid off of it.
You don’t have to be in a hurry to play the joker, especially early on in a hand. It will give your opponents too many chances of replacing it with a tile that they have in their hand. It is not normally advantageous to meld with a joker early on in a rack just for this reason. Remember, in the beginning you are trying to get as many chances at the drawing pile as you can.
Another way to place a joker in a meld that defensively will work for you is to play it only when you have the replacement tile in your hand. That way, it can never be replaced by anyone but you. You can always replace the protected joker at any time later on in the hand. This is especially important as you get to the end of a hand when you see that someone has only a few tiles remaining. You do not want to give them a chance to go out. The same works in reverse as well, but only if you have the protected joker. By putting it down early, only if it is protected, you are lowering your rack score just in case someone goes out. Since the joker is worth 25 points, you really don’t want to be stuck with it in your rack.