Here are my basic rules for playing post defense:
1. FRONT - Whether the defender is the smaller player or the bigger player, I never want my kids to invite the pass into the post. I teach them to fight for position and get in front of the offensive post player so that the entry pass can only be made via a "drop pass". This requires a low center of gravity and quick footwork. If the defender is the smaller player, then he has the advantage of having quicker feet. If the defender is the bigger player, then he will have a huge advantage once into position because passing over him will be most difficult.
2. PUSH THE OPPONENT DOWN LOW - Once the defender is executing the front, his goal now is to get as low as possible and start to push the offense to the baseline with his backside. Low man will have the leverage, and as I teach my kids, "low man always wins". This should be easy to accomplish because the offensive player at this point will be trying to usually abandon the front and will play tall in an effort to invite the lob pass from his teammate on the perimeter. This plays into the defenders hand perfectly. At this point, even a much smaller defender should have no trouble picking up valuable real estate in his attempt to box out his man under the hoop. Even just a foot or two gained by the defender makes the target zone of the lob pass that much smaller as well as that much closer to the help defense. The difficult part about this step is that their is not much time to execute the push down low. The opportunity will only last for a moment or two...
3. FORCE THE "DROP PASS" - Most offensive perimeter players at this point will not be able to pass up the opportunity to try and lob in a soft pass over the fronting defender. This "drop pass" might be the most difficult pass in the game to make. Despite appearing like a makeable pass, it has little to no success of making its target. First of all, it must be thrown is considerable touch and arc, this allows for the help defense to almost always have a shot at breaking up the pass.
4. INTERCEPT THE PASS - Once the pass is in the air, most offensive players will give everything they have to hold their ground and keep the fronting defender from pushing them off their spot. This is another moment that the defender must be instinctual in his timing. Once that pass is in the air and the push from the offensive post player comes, the defender can abandon fighting back, letting the offensive player actually fall away from where the pass is going. And that is when the defender must be quick with his feet and leap for the lob pass and try to break it up.
5. REBOUND POSITION - The one downside to the front, is that the defender gives up position for rebounding. Especially if he is on the weak side. This is a risk Im willing to take with my teams. If a front is executed to perfection, the offensive post player has been pushed close enough down low towards the baseline that his position for the rebound is minimized.
Whether you are the smaller player or the bigger player, always discourage the post entry pass by fronting. Make things difficult on your opponents. Because once they get the ball into the post and they have you backed down low on the block, the defender really is at the offensive players mercy.