How can I improve on my Defense in Basketball?

since your a big man its good that you can shoot threes i mean if you feel comfordible doing 3s do it. look at dirk hes 7 feet and drains threes as much as jason terry does but as of the defence, im a PG and ik that when im defending another PG i always look at his chest so that he cant fake me out and i always keep my hands up. it sounds dumb but i get like 3 steals per game because i put my hands up and when they try and drive on me i usually just step in front of them but if there too fas for you then let them past you and then look for the block from behind if there going in for a layup. if there a good jump shooter then just stay on him until he passes it away or you get help. also to practice threes pass the ball to yourself and then catch and shood real quick so you develope a quick shot. it gets ur ready easier for an in game situation