Keep your back angle constant on the way. This strengthens your six-pack muscles that lie on your belly: your rectus abdominis and your obliques on the side. . Your Back Squat wont increase if you only Front Squat. .
The weight will compress your wrists, bend them back and cause wrist/elbow pain. Keep your chest up, pinch your shoulder-blades together and squeeze the bar hard. If the spotter reacts too late, the pins always catch the bar.