It's honestly pretty simple, it comes down to controlling the things that you have the ability to control. Realize the Commander Ranking is not the largest portion of the calculation for awarding pilot slots. The ranking system takes into account the following: Grades, PFA, PCSM (AFOQT/TBAS/Flying Hours), Field Training Score, and Commanders ranking.
Grades: Totally under your control. Study, do homework, do the extra credit stuff.
PFA: Get 100, or as close as you can. Start working out now, don't be that guy trying to get in shape 2 weeks prior. It won't work.
PCSM:
-AFOQT: This test isn't hard if you study for it. Get your hands on a study guide (you can find them on Amazon) around a month before the test. Look it over once every few days. 2 weeks prior to the test, do a practice test a day with time restrictions. Do that, and you will be fine.
-TBAS: Honestly this is hard to prep for. There is a small section that you can prep for by finding some online materials, but the rest of it is just testing your reactions.
-Flying Hours: I got 11 flight hours which helped my score a little. Some people got more, some less. It comes down to what you can afford. If you have the ability I would suggest getting a few just to introduce you to the mechanics of flying, but there is very little cross over to actual UPT flying.
Field Training Score: Prep for it, be a good dude, don't be a DG hunter. If you don't get top third don't sweat it, the important thing is being a team player.
Commanders Ranking: You asked what will set you apart? Refer to above comment. Be active in the det as long is it doesn't affect your grades. Volunteering for everything means nothing if you get a 2.5 GPA. Study what they tell you to study. Help your buddies out. Don't be a DG hunter.
The huge majority of your score is under your control. Keep grinding, stay humble, be a good dude, and that attitude will get you far.