To get better you need to be taught and take it all in. Well, when you're young and first learning you may forget some things your coach taught you.
So, coaches I recommend you to offer volleyball study guides. These guides can be on many different things though. If you're coaching young kids, I would give them a guide on all the rules and some volleyball vocabulary like serve and pass. Now as you get into middle and high school these study guides could be like the rotation you're running or even just some exercises you recommend they do every night or ever so often.
If you're coaching high school or a high school club team you may want to also give your team a set of the volleyball rules they will be playing by and some drills they can do at home. This will only help them learn things at home so you don't have to take extra time out of your practice to explain things in detail.
Some simple drills can be as easy, such as going over your spike approach steps or doing 100 sit ups a night. Or they could be a little harder like running a couple miles or doing a lot of reps of one thing. You should also make sure the team knows the terms like pass, set, spike, etc. Also, make sure each position knows their code name to get a set as well as the setter.
Well it's up to you if want to give your team volleyball study guides or not. However, it wouldn't hurt and will only help out the kids who may be a little lost.