Start slow, take your time, and you might be surprised at how well you'll do!
The Glock trigger is different than most other trigger actions, but the fundamentals are still the same. Hold the weapon firmly, align the sights properly on target, hold them as steady as possible (they ARE going to move around a bit; don't worry about that), and make sure you squeeze the trigger gently ALL the way through the squeeze (especially at the "end" of the squeeze, when the weapon is about to fire). If you do these four things, the bullets should pretty much end up somewhere near the center of the target. If you start seeing low shots on target, take more time with the squeeze. "Pulling", "jerking", or "slapping" the trigger is bad, and will make the weapon move a bit before the bullet leaves the barrel. After you've formed and ingrained good trigger control habits, you will be able to speed up your shooting without jerking and missing the target.