reffing the screens

[cloverdale]

Hi everyone been away from the game since Febuary and just did a varsity team camp...one of the things I want to work on for the up coming season is to do a better job of reffing the screens and the defenses that have to go through them...as I tried to pay attention to more of the off ball I still was struggling with the screens and was wondering is there a trick to slowing down the action in the paint>?