Oh cool. I started one at my high school last year and it worked out pretty good and it was a blast! We just figured out what days and times people could meet, found a club adviser, and a classroom we could use. Since about 6 of the 15 members were the only ones who could play the uke, we just found a bunch of songs we liked and played them while everyone else sang. Then we also taught each other how to play.
I guess what would be a good like motivation for the club is to do a performance of some type. Our club decided we would enter the talent show which pushed us to practice and work together.
Hopefully this helps ya a little and it wasn't too boring to read! Good luck!