We ask (strongly suggest!) that at least one parent be at all of the practices the first two weeks. We particularly get the dads to help by holding blocking dummies, or lining up kids for drills etc. This kinda gets the old man's juices flowing, and the next thing ya know, you can't keep them away!

Sorry - this answer was supposed to be posted in a different question about how to get parents to become more involved in team practices.