For me:
Color: Black - Even though the white looks nice, I just prefer the black
Capacity: 64GB - Since I'll be getting my first iPhone this summer, my iPad will replace my iPod Touch as my mobile media device that I keep everything on (all my movies, tv shows, etc.). Since I'm already over 32 GB on my Touch, 64 on the iPad is a given.
Model: Wi-Fi+3G - I don't plan on using the 3G on a regular basis, but I can foresee situations where I will enjoy having it.
Carrier: Verizon - 3G service will mostly be used by me on trips and since I travel fairly often around the country I want the widest coverage possible.