In a scoring game, patience is a virtue. In standard block or draw games that don't keep points, the key is getting rid of your tiles. In a scoring game, it can be wiser to hang onto a tile rather than play it. This is because of how the board count changes with the laying of each tile.
Since new pips are added to the total every time a piece is put on the board, you'd think that the board count increases with each player's turn. This isn't the case: When a pip is hooked to another pip, they sort of cancel each other out. Only unhooked pips contribute to the board count. In other words, take another look at your tiles before you play them.
Consider this scenario: You're faced with a board that has a 10-point count and one of the open tiles has six pips. You have a tile with a six-pip end. But before you play your tile, look at the other end. Let's say it's a three (which would make it a 3-6 tile). If you hook the six end to the open six on the board, you'll end up removing three points from the board, since the sixes will cancel each other out. The original board count of 10 loses six points when you hook the six. This leaves a board count of four, plus the three you added with the other end of your tile leaves you with a score of seven for the round.
In this case, it would be better to hang onto your 3-6 tile until a three opens up, which will give you a chance to add three to the board count.
It's difficult to pass up what looks like an obvious play; since you're giving up points, you may still want to take the seven points by hooking the 3-6 to the open six. You can see that it takes some mettle; in some games where a timer's used, a player also needs nerves of steel.
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