One of my go-to reads in the off-season is "Winning Defense" by Del Harris. It's a great read with detailed concepts from an outstanding defensive coach and should be a part of every basketball coaches' library. Here are some of his thoughts on switching:
Four Basic Guidelines For Switching:
1. Switch with teammates of equal or near-equal size on screens and crosses.
2. Switch to keep big players inside and small players outside on screens. Do this on changes and crosses away from the ball when possible, and on matching up in transition defense, as well as in recovering on rotations. Any communication that can allow a switch to accommodate the big in-little out concept is usually worthwhile.
3. Switch within fifteen feet of the goal.
4. Use the “emergency switch rule.” That is, switch whenever a situation arises in which a switch will challenge an open shot, regardless of the mismatch as X2 does for X5 in D-60.
Communication. Even though we have rules for switching and a game plan to dictate in which particular situations we’ll switch against a given team, no switches are considered automatic. Players must physically come together when possible and call out verbal signals such as “switch”, let me through”, “stay”, “get through”, “I’ve got high”, “you take low”, etc. In addition to the verbals, it’s necessary to use the hands to point and pull or push each other through switches and stays when necessary.
Switch and deny should be considered as one big word- “switchandeny”- because both actions go together when done properly. That is, when there is a switch, something must be denied to each offensive player involved in the switching. If neither one has the ball, the defenders switch aggressively to stay in a position to deny each one the next pass. If one of the players has the ball, the defense works to deny the pass to the one who does not have the ball and to deny an easy shot or route to the basket to the one who has it. This helps prevent the laziness in defense that can occur when a lot of switching is used. Accepting this point can help players better understand that switching is not an easy way out of performing hardnosed aggressive defense.
Areas where most of the switching will be done. The backcourt is an ideal location for switches and pre-switches. (The latter is a switch done ahead of time by two players inverting their assignments because they know there is a high likelihood they will be switching anyway. This way they do not have to try to get back to their own men in the frontcourt.) There is plenty of time to get rid of mismatches that occur 80 feet from the basket and a lot of time can be wasted by the offense in the backcourt as the offense struggles to bring the ball up against a good, aggressive switching defense.