Prepractice meetings, especially if it is a summer schedule not interfering with school time, need to cover the basics on every new Concept. This is not a time to teach the individual techniques for each position but show what the concept looks like as a whole. If you have video showing the video and using a board are extremely important. Walkthroughs are key during this time, Quarterbacks need to warm up but that can be handled by them getting out right after the meetings. Walk through every new play that will be installed each day against what your base defense looks like and have your Center Identify the front and make all calls, i.e. F calling the Pass Pro and WRs IDing Most Dangerous Man. Again, this time is not to be used for teaching technique but so that players can now Walk Through their role that they learned on the board and with video. If it is a pass play have the Q identify his read and call out his progression. If it is a run have the Line call out their blocking assignments, Q ID his read (if used), and F ID the Running lane and bounces. After walking through each concept try to get as many 2s and 3s into the mix as possible. Best practice is line up trash cans or position coaches in the base defense you will see that day. Try not to use players so that they can take the mental reps behind the 1s.