Protect Your Pieces
It helps to not lose your pieces without justification. A reminder for points is the queen is worth 9, rooks are worth 5, knight and bishop and worth 3 and pawns are worth 1.
When your opponent makes a move it's always good to see what he is threatening. An easy way to do this is to think at the start of your turn "if my opponent could move right now without me even getting a turn what would he do."