I was you about 13yrs ago, except heavies not fighters. Here is what I did....
1)Hit the gym. AMS (I think its all OTS now???) day one is a PTtest. USAF PT tests aren't that bad, but you have to past or you go home.
2)Don't think about flying, you will get plenty of that really really soon. I wouldnt pay for any ratings.
3)get a low stress job if you aren't currently employed. I waited tables. Best job I have ever had. I was single and got more action there then my 4 years at an SEC college! Training is stressful. It is designed that way. Relax now.
4) take money from #3, max out Roth IRA (EVERY year), and pay off any debt.
You will thank me for this later, I promise.
5) get enlisted in your unit and burn up all the UTAs you will miss in training. Pick the brains of the guys fresh out of training. See what they would have done differently.
Good luck!