Do well in your classes/rotations, get research published if you can do it while also doing well in school. If you're not a goon, do an away rotation at a military residency into which you're interested in matching. Narrow down your choices. Neurosurgery, Neurology, GI, General Surgery, EM is kind of a shotgun approach. It's fine if you're early in your training, but eventually you'll have to make a choice. Until you do, the best thing you can do is to stay on top of your grades and your rotations.
I'll tell you how much military bearing and PT test performance meant in my residency: absolutely nothing. If you were a jerk-off personally, military bearing or not, then you were boned. But no one cared even in the slightest how well you did on your PT test. Certainly if you got a 300 every time (and one of our residents did, and still does to this day), then people would remark about how that was kind of impressive. But we had plenty of residents who got nervous every time they took a PT test. I never failed one, but also never came close to maxing, and I was in a highly competitive subspecialty program. I'm sure there's some variability between programs. Maybe EM or Ortho find PT test scores more appealing than we did. But if you're a bad student, then it doesn't matter how well you did at PT.
Get your bases covered first. If they're solid, and you're in range to max a PT test, then go for it. But I wouldn't break out a ton of time in your schedule to make that happen. MODS says 50% determined by military show of commitment - either that means USUHS or it's just fabricated BS to over-emphasize the importance of military bearing. It would not surprise me at all to find out it was the latter. So unless someone can tell you how they measured that, I wouldn't put much stock in it.
Don't get me wrong, if you have two residents who are complete carbon copies of one another, but one had a 300 on their PT test, then sure, that guy will match. But that's not a realistic scenario.