A good technique...which many of you will know

A good rule of thumb is: when you are ahead in material, trade down.

Near the beginning of the game, if you are ahead a Bishop, you might have a total point count of 39, to your opponent's 36. But, if you trade most of your pieces evenly for your opponent's, you could end up with, say, 5 points to your opponent's 2.

Imagine a basketball game... you could have 39 players to your opponent's 36, or 5 to his 2. What an advantage! Although the numerical difference is the same, your extra players would determine the outcome of the game. The same principles apply to chess. After the trades, your extra Bishop could capture the remaining enemy Pawns, then you could promote one of yours to a Queen, and finally, execute the enemy King.

Yes this is what I try to do if I'm ahead in a game. Trade off the pieces evenly and the advantage gains strength near the end of the game.

Of course the reverse is true; if I'm down near the start I generally try not to trade pieces if my opponent offers.