Re: Most Important Skill(s) Coming Into A Team?
Personally I view the most important skills for FRC is effective communication and teamwork. They're great skills beyond just the scope of FIRST.
But if you're really looking for just plain hard skills, for people coming into FRC teach them:
1. Building with safety in mind (this can be through building something like a kitbot and walking them through the steps)
2. Basic design (this can be through doing a classic catapult competition)
3. Game analysis (have them finish the program by analyzing an old game and come up with a basic robot strategy and idea as a team to simulate kickoff)
Skills like CAD, programming, and design based on gearing/physics/etc should be learned when they're actually on the team during the offseason, rather than during a week long summer camp.
Like others have said, make the material broad, don't try to dig deep into the technicalities since this will most likely be the first foray into robotics for most kids. Make it inspiring and encouraging.