Devise CD scavenger hunt challenges that will demonstrate just how useful CD can be. Lurking is how most people get started anyway.
If you have members with special interests in mechanical, electrical, pneumatics, etc. challenges could be interest based:
- Mechanical: uncover plans on how to implement two new drivetrains.
- Electrical: plans for two different systems to control balls this year.
- Programming: ways to integrate a particular type of sensor
- Pneumatic: alternate layouts that each weigh less than it's predecessor.
Make some easy just to get them started, later ones could be based on what you might want to try during the off-season.
Maybe pick a problem that's known and been discussed, so the new members have to locate where possible solutions are discussed.