The squat-through vault is one of the basic fundamental skills that stand as a stepping stone to harder vaults like the handspring. Learning the squat-through correctly can make future skills easier to learn.
Like all vaults, this begins with a run. While a fast run isn't essential here, it certainly will make it easier. The squat-through is performed the best when there is a lot of horizontal momentum.
Next is the hurdle. Hurdling too high will make you lose some of your energy, so remember to keep it long and low. Begin your hurdle half a step back if you have to. This is one vault where you should not punch on the board with your feet in front of you. You should hit the board with your body vertical, or slightly leaned forward. This way, you can get your hands on the horse with the speed you got from your run. If you have too high of a pre-flight, you won't have enough forward momentum to get you over the horse.
The next part is trying to get your feet up and in between your hands without touching the vault. Most people think they should tuck right after they punch off the board, but this causes you to lose a little momentum. As you reach out in front of you for the horse, keep your body straight, and when your hands hit, that's when you begin to tuck. What's important here is to lift your hips so you can tuck your legs and get them over the vault. But be careful not to lift your hips too high; otherwise your legs come straight back down on the vault. With a spotter, practice trying to get over the vault with just a few running steps. Get a feeling of what's too high or too low.
Once you're sure your feet will go over the horse, it's time to finish the last phase of the vault. To make sure you land on your feet, push up off the horse with your hands, and as your body begins to straighten out of the tuck position, lift your chest so your body lands on the mat in a vertical position.
Keep these tips in mind as you work on your squat-through vault. Keep practicing, and good luck!