The old school method of boxing out even if the ball hit the floor belongs in the history books with the two handed shot. The 3 point shot pulls defenses so far away from the basket that creating a "shell" is impossible. Having guards run out to the 3 point line to try to box someone out is silly. Also, long shots lead to long rebounds, making the shell more useless. I have my forwards box out, and then everyone else bumps a guy and goes after the ball.
I want the box out to set up around 5 feet. If the opposing player wants to stand under the basket, let him. Aren't a lot of rebounds right under the rim.
On the offensive boards, I like crashing rather than position rebounding. Do not engage with the defender if you can avoid it. The defender is already between his man and the basket, so he starts with the advantage. Don't try to out muscle the defender because then he knows where you are. Avoid contact with the defensive rebounder if possible.
2-3 zone defensive rebounding is tougher. The baseline players have to find a body, because all it takes is one guy not doing his/her job and there will be a lot of second chance shots.
defensive rebounding is a challenge in 3-2 and 1-3-1 defenses. Communication is really important in those defenses because a lot of times players don't even know the shot is up.