Do you ever find yourselves relatively decent chess players, losing against total patzers? Do you leaves those games thinking. "Man, I know I'm WAY better than they are - how did I manage to lose?" Ah, this is a well-known phenomenon!! For some reason, playing against weaker opponents has a way of bringing out the worst in one's own play.
For this reason, a lot of chess players recommended NOT playing against weaker opponents.
In general, I think this is good advice since playing against better opponents will push you to improve your game. However, it would still be nice to be able to beat weaker opponents on these occasions when you do play them! Here are a few pieces of advice for this, which might help.
First of all, I notice that when I play against weaker opponents I foolishly assume that I am going to beat them without any problem.
As a result, I don't play carefully enough and I end up making stupid mistakes. Or I just plain hang a piece, allowing my opponents to capture it free and clear.
The key to overcoming this problem is to force yourself to play as a carefully as you would against Kasparov; no matter how bad your opponents are; always assume that they will play the best moves.
Second, significantly weaker players often make moves, which are so bad that they make no sense! As a result they create positions on the board, which defy the pattern-recognition skills that you, as a sophisticated chess player, have developed.
Such positions put you in "uncharted territory", in a manner of speaking; since you can't rely on your pattern-recognition skills in these sort of situations, you have to interpret the position right there and then over the board.