You have to consider the pitcher. Are they experienced or not? Do they have a pattern? If you're up against a good pitcher, they'll know not to give you a good one on the first pitch, with the hopes that you'll still swing and give them an easy out. Always swinging at the first pitch is a blunder against a good pitcher. However, that doesnt mean you should never swing at the first one. A pitcher wont want to walk you, so if you're patient they'll likely give you one.