page seems to be broken right now, but usually works. Has the different WO MOS, requirements, packet to fill out, etc...
FIRST, you need to figure out what you want to do. There aren't any Infantry Warrant Officers, so that narrows your options down. You'll have to find a field you'll like and transfer to that MOS to get the experience then go Warrant.
Unless you're talking helicopter pilot (153A), any MOS can apply for that one.
There are a few others that will let you in- such as Signal (255A or 255N), but you must first get the training or civilian experience.
For pretty much anything except Pilot you must get into the right MOS then work in that MOS as an NCO a few more years to get the experience. There IS an SF Warrant Officer position, you'll have to see what the requirements are to get into that one.