Well, I'll toss in my two cents.
At the JV level, most of your players have been playing a while. They all have their style and routine to their basic skills. It may be good, bad, or ugly, but it is how they do it. Unless their form is really, truly, god-awful terrible, it's not worth it to break it down their muscle memory and rebuild from scratch. Even then, the kid has to be really dedicated or it won't work. Usually you can just tweak their mechanics, and there are drills and warm-ups you can look up that will help tweak them in the right direction.
Watch. Watch, watch, watch. Watch college softball - early season showcase tourneys will start pretty soon, and ESPN will probably broadcast a couple of games. The announcers on those are usually former high-level players, and they will often talk about useful little nuances of the game. Watch how it's done when it's done really well. Watch baseball if there's no softball on TV. The game is different in execution, but a lot of the ideas are the same. Especially spring training or early season games, if you can catch announcers chatting about how players may have worked on their game in the off-season. Watch training and coaching videos, like other people have said. Watch your players. If you see something that looks off, watch them do it a couple of times so that you have time to really see it and think about what the root of the problem is.
And watch the ball. It's the dumbest, most useful advice you can give for hitting or fielding. Don't just sort of see where the ball is: LOOK at it, actively point your eyeballs at it, and focus on it. Watch the ball.
ETA: Lots of college softball broadcasts archived on YouTube. ESPN isn't carrying much of the early February games that I can tell.
ETA2: If you're anywhere near the northeastern corner of the state, see if you can't drag pinotbear out of Massachusetts to help out. He golfs too much.
