I'll tell you what I do. Pro or All-Star, doesn't matter. Same principles apply.
1) For nine hitters, the first time through the lineup, I always take the first strike before I swing at anything else. This helps to ensure that the pitcher throws a decent amount of pitches early on so that he's softened up later in the game. Go through the lineup twice taking the first strike if it suits you. *Sometimes* I will break my own rule and swing at the first strike early on if the pitch is a nice red meatball down the center of the pipe.
2) Play your batter's hot zones, if you use them. Before the pitch think "I am not going to swing unless the ball is headed to this spot". And stick to it. Once you have two strikes against you, then swing at whatever's in the strike zone. Usually, I go though this type of process: 0 strikes, I'm only swinging if it's coming right here. 1 strike, I'll swing if it comes here, or here. 2 strikes, swing at anything in the strike zone.
3) Pay attention to the types of pitches thrown, and watch them come off the pitcher's hand. This will help you to gauge what it is, and where it's going.
4) A no-brainer, but, swing where the ball is going, not where it is.
5) Just play, baby.
The more you play, the easier it gets.
Hope it helps ya.