I'm 5'7" so I'm not really worried about rebounding or boxing out. But I do play postion, allways. Whenever the shot goes up, I try to get to the opposite side of the basket from where the ball was shot, looking for the carom. Also, most people do not have good hands, you'd be amazed at how many balls you can take right out of a taller players hands.
After a while I become a big distraction to the big players around the basket, if they get passed the ball, I try to get a hand on it. If they try to dribble I take it away. They become so worried about where I am, that they stop playing ball effectively.
The only secret is being quicker than the other guy and getting to the spot you want to be at. Also, be aggressive like Charles Barkley, go, go go, relentlessly and you will get more than your fair share of boards.