Tomorrow: Rent a bike in Amsterdam

  What do you call people from Amsterdam?
  Amsters? (Heh, like British hamsters. No.)
  Dammers?
  Dams?
  Amsterdammers?
  Okay whatever.
  Where is the best place to rent a bike in central Amsterdam?
  I see Mac bike rentals everywhere. But they look like pretty plain bikes. I have a Giant back home. Probably don't need so many gears here. I've also seen Yellow Bikes around town.
  Any advice?