Getting a Cav Platoon as Armor Officer in the Army?

I'm in ROTC right now and thinking out my wishlist ahead of time. Right now, my top three are Infantry, Armor, and Field Artillery (interested in something combat arms related as you can see). Basically, just wondering how I can better my chances of getting a Cav platoon if I branch Armor. Do you get a duty-station wishlist like when you're enlisted when you're commissioning? If so, does putting down a duty station like Campbell, Drum, or Bragg better your chances of getting a Platoon of 19D's since those are light units? Any help is appreciated.