What ways are there to raise rank in the air force?

Question

Just enlisted i have 16 credits thinking about taking a few classes to get to E2

Answer 1

You had to come in with those credits to be an E-2.

Are you in DEP maybe?

I came in as an E-3 because I had 45 credit hours (you need 44 to come in an E-3).  

Answer 2

You can't do anything to get E-2 early, that goes for E-3 as well.  If you are able to take a few classes (depends on if you're done with your CDC's and if your squadron will allow you to take classes) and you are an outstanding airman then you could possibley put on E-4 early, which is called BTZ (Below The Zone.)  Also volunteering helps out (for everything not just military stuff,) this could help with getting more medels or medels that are worth more points when you test for E-5.  Firewall 5's on your EPR's help as well.