A screen or "pick" occurs when an offensive player attempts to block, or "screen", a defensive player away from the man he is guarding, thereby freeing up that offensive player for an open shot or pass. Setting good screens (or "picks") is a very important fundamental part of the game. It is often assumed that players will know how to do this, but like any other important fundamental, it must be taught correctly. Screens are most helpful in freeing up a teammate against a man-to-man defense, and in out-of-bounds plays, and there are often times when you want to screen a zone defense as well. Setting good picks are basic to most offensive plays. Oftentimes, it is the screener that gets open (after sealing the defender). So setting a screen is a good way to get yourself open for a pass and shot. The "pick and roll" is still one of the simplest plays, but when done correctly, one of the most difficult to defend. The Utah Jazz's John Stockton and Karl Malone were masters of the pick and roll.
2. Be strong. Get your feet wide and plant your feet solidly. Do not move your feet once you have established this position or you will get called for a "moving screen" (a foul). You must be stationary and not move with the defender, and you must not push the defender away. If a defender bumps into you and you are not stationary, you will probably be called for the foul.
3. Keep your arms tucked into your chest, not only to physically protect yourself, but also so the ref can see that you are not pushing with your hands, or grabbing or holding the defender.
4. The angle, or direction, of the pick and the timing of the pick are probably the most important, and most overlooked factors in setting a screen. You must have the correct angle, or position, when you set the pick. You must anticipate the direction that your offensive teammate wants to go, and then make contact with his defender in a position so that you are directly in the way of the defender, and he/she cannot get around you. If you don't get the right angle, the defender will simply slide around you. Perhaps this is best demonstrated in the diagram. In Diagram A, the screener does not make contact, and the defender slips behind. In Diagram B, the pick is too high ( a common mistake), and the defender slides behind the pick and stays with the defender. In Diagram C, the pick is too low, and the defender can fight over the screen. Diagram D shows a good pick, followed by screener "rolling" to the hoop.