I practice concentration all the time. You do it by picking something small and concentrate on trying to see the smallest part of it. It can be practiced anytime watching tv,out in the yard, anywhere, the more you do it the better you will home in. Also if you are shooting at a bag target with all those dots on it, cover the target with corrugated or paper and only put one 1" dia. dot on it and practice with that. It takes time but soon you will be shooting a whole bunch better. Remember this is sight work not form work, so always practice form first than sight. You cannot concentrate on a tiny spot if you have questions in your mind about your form so take care of that first before all else.