Once you finish college, your options are limited. One is to apply to the USAF/Navy/Marines for officer/pilot training, get selected, and then finish in the top part of your pilot training class. This is all very competitive, and there are no guarantees of making the grade for fighters, but there are commitments once you sign up. The other is to find an Air National Guard unit flying fighters that has an open pilot training slot (usually 1-2 per year per unit), apply for it, get selected (usually a dozen or so applicants for each slot, and those with pre-existing ties to that unit have a strong advantage), and then complete USAF pilot training with high enough grades to qualify for fighters.
As for prior training, my experience 40 years ago was that those with significant pilot experience had a strong advantage in pilot training. One of my AOCS classmates was a graduate of Southeastern State's pilot program, and spent a year as an aerobatic instructor there after graduation. He aced the program all the way through, and was the first "nugget" selected for F-14's when he got his wings (up to then, you needed 500 hours of F-4/F-8 time to apply for the F-14).