Read everything on the USAFA website, every link, every draw down. Take notes.
Search "chance me" and "stats" threads on all SA forums here to get a feel for what others are doing/have done, and the scope.
Read up on nominations, sources, Academy Information sessions, on primary sources. Read the Nominations thread here on SAF.
Read the Acronyms Sticky here on SAF.
Build out timelines, identify action items. Develop a plan that addresses every aspect of your future application. This is a marathon, not a sprint.
Research your Plans B, C, etc.
Be sure you want to be an Air Force officer, research the career fields available to officers, and work backwards from there to find the path that best fits you.
Read the DODMERB forum and threads related to medical DQs. Get smart on any conditions that could be a problem or medications you might have to be off of for a specific period of time.
Explore the other SAs, to develop clarity on your decision, and to be able to confidently answer the question "why didn't you apply to X?"
Look up the CFA and assess where you stand with regard to the averages. Much easier to ramp that up a few years out than 3 months prior. A good resource:
http://www.stewsmith.com/linkpages/serviceacademycfa.htm
Think carefully about your rising senior summer, and the scheduling challenges of trying to attend the USAFA summer program, Boys State, Girls State, etc.
Don't do anything foolish! Exercise impulse control and stay focused on the long game here. Keep your social media respectable.
Visit USAFA!