The pick and roll is half of pro basketball offence. It's also the play most amateur teams run worst. Four reads fix it.
The set-up
Your big (the screener) walks up to set a screen for the ball-handler. The screen is a stationary obstacle — the screener can't move into the defender, can't lean in, can't shift their feet. They plant and stay. The ball-handler reads the defence and reacts.
Read 1: the defender goes under the screen
If the defender on the ball cuts behind the screener (chooses the easier path), the ball-handler should pull up for a shot. There's no defender between them and the basket — take the shot or attack the closeout.
Read 2: the defender goes over the screen
If the defender fights through the screen, the ball-handler turns the corner and drives to the rim. The screener's defender will jump out to stop the drive — that creates the third read.
Read 3: the screener's defender hedges or switches
When the screener's defender steps out, the screener "rolls" — sprints to the basket. They are now wide open momentarily because their defender is committed to the ball. The ball-handler delivers a pocket pass or a lob. This is the actual scoring action of the play.
Read 4: the help defence rotates
If a third defender rotates over to help on the roll, that means someone the help-defender was guarding is now open. Kick the ball out to that shooter. This is how pick-and-rolls generate three-pointers.
How to practise it
Two players, one screener, one ball-handler. Run it ten times against passive defence to learn the spacing, then ten times against active defence to learn the reads. The four reads above are the entire universe — there's no fifth thing to learn.
Find a court with three friends and run it for twenty minutes. Your offence will look completely different by the end of the session.