If you watch and listen to professional tennis on television you will often hear "serve plus one or return of serve plus one" mentioned.
Today's best players focus on and try to execute a good serve or a good return of serve as well as a good first shot following the serve or return. Most of the points are won with one of these shots and the player who successfully hits the first two balls well more often is almost always the winner of the match. This idea seems extremely simple. However, pay attention next time you play a match and keep track of the number of points that you are able to execute the serve plus one or return of serve plus one as you had planned.
It is likely that you will have a high number of successes if you are winning the match or a low number of successes if you are losing. Keep the focus on these first two shots and once you have gained some consistency with this idea, you can then move on to "how can I finish or win the point".
More often than not, you will not even reach this stage of the point so make sure to emphasize and focus on the first two shots that you hit.