[evanperryg]

My team has grown rapidly over the last few years. As a result, we've had to learn how to handle a lot of people, teach them about FRC, and maintain efficiency in a tiny shop with 45 people (we get about ~20 new members per year).
Basically, read everything ttldomination said. But, remember that none of those methods work if they are used in groups of one or two. Keep your teaching methods diverse by combining enaging sit-down presentations with hands-on work. This way, you will cover most of the ways a typical student learns. My team teaches new members through powerpoint presentations (you might be able to find my 2013 electrical training powerpoints somewhere), small-scale competitions, and construction of full-scale FRC robots.

Presentations: Powerpoint presentations and the like are good for providing an overview to new members. However, they can get boring. You MUST get engaged with the new members, and make the presentations interesting.
Mini Competiton: FTC and VEX are good options for small-scale competitions, but you should also look around for competitions held by local teams. New 2338 members participate in a vex-scale competition held by team 1625 each year.
Full-Scale Robots: The best way for programmers and electrical(ers?) to get pre-competition experience is to work with real FRC robots. Take a robot from a previous season, and have new mechanical members strip it down to the frame. Have them put a couple of the basic attachments back on the robot. Then, help electrical team students wire that robot, even if it's just the drivetrain and a piston or two. Once it's built, hand it over to programming and they can program it. Real experience for each of the 3 biggest subteams.

Remember, nobody can learn everything there is to know in a single pre-season. After their first FRC season, there is still a lot young members can learn. During the summer, continue showing new members more advanced concepts.