Two things will help you identify pitches. The first is experience. Like anything else, the longer you pay attention to it, the easier it will get. 
     The second is this: watch the pitcher warm up between innings. (Obviously, you can’t do this on TV, so you’ll have to do it at a game.) He’ll signal to the catcher what he’s going to throw before he throws it. If he sweeps his glove up toward the catcher, he’s throwing a fastball. If he shows the catcher the ball and brushes it down at an angle, he’s throwing a sinker. If his glove comes up and over with its palm up, he’s throwing a curve. If he sweeps his glove across, he’ll throw a slider. And if he shows the catcher the palm of his glove and then pulls it back closer to his body, he’s signaling that he’s going to throw a change.
     Watch this between a few innings, and you’ll be surprised how quickly you’ll be able to identify pitches once the action resumes.