Your opponent's good move is your good move
It may often be useful to think about what your opponent would like to play if it was his move. If it is a good thing for your opponent to get something, it is a good thing for you to stop him from getting it. To stop him from playing on a point, you can play there yourself.
Note that your move need not always be exactly the same move as he would have played. Rather, it often is a move in the same general area. Still, one can often settle the issue of who gets a key point simply by occupying it yourself.
See for example: