Post players are becoming less aggressive in youth basketball over the past few years. I have seen many referees call some really bad calls and coaches screaming about a foul because the other teams player is posting up his player due to the lack of knowledge the coaches and referees have these days. In Basketball you are allowed to post a player up anywhere on the Basketball court. the post game in not only for the low post but can also be used by a guard trying to dribble the ball up the court. 

How a Center Posts Up: 
This is the back to the basket skill you hear the commentators talk about on TV. A center can use his butt and hips to get an advantage over your opponent while using one hand to feel for your defender and the other hand asking for the ball. When posting up you can feel for where your opponent is but you cannot push or pull. 

How a Guard Posts Up: 
Many Guards have no idea how to post up and protect the ball they're defending, this can really take away from the players game. A guard must know how to post up a defender so the he/she can protect the Basketball. A Guard posting up is much of the same technique as a Center posting up, however, a Guard will not be looking to score off of posting up his defender but rather protect the ball he is dribbling from being stolen. When posting up another Guard you need to remember to look from side to side for a safe pass to be made or else another player will come from behind and steal the Basketball.