This may not always work, especially if you play against strong players, but if you play with weak players, no matter what age, you can fool them. The trick is to leave a piece hanging (unprotected) while pretending not to know.
Think of a plan. Usually, when you fool an opponent, you should sacrifice a piece for more value in the game or an easy checkmate. Suppose your opponent is black and castled king-side. He has not moved the rook or pawns and your queen is pinning the center pawn.
Your bishop is about go to [h6] and prepare for checkmate when your opponent prepares to take a protected piece with all safety measures possible, but if he takes, he will lose defense to his king. What do you do?
If you move the protected piece, you lost a move, but if you move the protector, you can win. So you move the protector to some other hanging place(it would be the best place to move it) and your opponent takes the piece. BAM! Your bishop threatens mate at [h6] and your opponent is hopeless.
Think of a way to trick your opponent. If your opponent is weak, you could just leave a hanging piece and he/she might fall for the trick. If your opponent is strong you might need a little more than a hanging piece.