I've never run an official 9:12 but I just did a week ago without seriously prepping for it. Take my advice for what it's worth...

The first thing you need to do is get on a pretty strict diet. You're not going to run that fast with a bunch of extra fat on your body. What worked for me was using an IIFYM (If It Fits Your Macros) calculator and sticking to the diet religiously. I intentionally "bulked" up to 220 pounds and I was big and strong but my cardio sucked and my knees started to hurt me. At my lightest I was 178 which felt like I was running on the moon.

Second, go to the HAWK and get a running assessment done. If you don't know what type of runner you are/what type of feet you have, it could really be hurting your runs.

Third, never run more than 3 miles if you're preparing to smoke a PT test. I ran two miles two times a week as fast as I could, one day of sprint work, and one day of running one lap as fast as I could with a two minute rest 6 times. You need to figure out what a 1:30 lap feels like and get yourself used to running that speed; even if it's only for one lap at a time. Once the one lap at 1:30 starts to get easy, start running two laps and try to come in under 3 minutes until you get to the point of running 6 minute miles. Also, get on a lifting routine where you're working out 4-5 times a week. It'll help your overall health and your cardio.

Fourth, create a playlist that is exactly 9:12 and try to figure out what song is playing when you hit the 3 and 6 minute mark.

Fifth, try taking some caffeine before you actually test. Don't go crazy and take 1,000mg but 200mg should be fine.

Sixth, ask to do your run first. In the PT reg it states that you can take the test in any order you want and the FAC can't stop you from doing the run first. For me, running after doing pushups and situps sucks and my legs feel way more tired.