I have a young horse that is floating too far away in his approach and just making his pocket too big.  Does anyone have any exercises to correct this?  Thanks

I don't have an exercise but put a cone at the pocket so he has to go between it and the barrel. That may help. 

Most of the time when they float out its due to no hip control or the rider not looking up and actually driving straight to the entry point or perhaps leaning and pushing them out with their weight or dropped shoulder. If it's no hip control the horse is just following its shoulders to a wider path. I would ride straight to my entry point and kick the hip to the inside. You can't just start doing this and expect the horse to understand what is being asked. You need to teach hip control off the pattern starting with a step or two all the way up to moving their hips in a circle around their front end. You need to be able to walk, trot, lope and ask that hip to step over. This move will teach them to keep their hips under them and be the driving force thru the turn.

A LOT of people ride their horses straight to the pocket but then let the horse step out to make the turn. Make sure you are not doing this in slow work. Just one step out can theach them this bad habit. They always increase their reactions with speed and pressure so 1 step at a walk is 3 steps under pressure.

I agree with a cone also. Visual aids not only help the rider be consistent but they help the horse understand what is being asked. Consistency is key.

Square turn. Pick the size pocket you want , keep him between the reins, no  arc in his body. Sit square.

Thanks everyone!  I will try all your suggestions:-)