Meet APFT and height/weight standards. Other than misconduct, these are the only reasons they can fail you from the course. If you are not used to running, or are only running enough to be able to pass your APFT, you need to run more. We had a significant number of overuse injuries due to students not being accustomed to the volume of running. There were many, of course, who thought our PT very easy. Compared to other BOLC courses, AMEDD PT is a piece of cake.
You will be ridiculously hot when you go to the field. More accurately, you will be dangerously hot. Our class just came back from the field and we had a student fall out due to heat injury nearly every other day. Some went to the clinic, others were hospitalized. Aggressively hydrate, eat your damn MREs, and seek out the shade. If you do start to have s/s of heat injury, identify yourself to cadre sooner rather than later. The ice immersion baths for your arms saved my ass on the M16 range.
Your class is, reportedly, gigantic. Really. Ours was 300+ and we heard yours could be nearing 700. Seems impossible, but they will find a way I'm sure.
Prepare yourself to hurry up and wait. Don't let yourself get frustrated with "wasted" time or wrapped up in how this or that could or should be done better. Take a few breaths and just drive on. We had a lot of people in our class get pretty bent out of shape at one point or another over relatively little stuff. The logistics of a course of this size are daunting, and your cadre are only so many.
We built a couple of the tents you all will be sleeping in during the FTX. You will have A/C, showers, port-a-potties, and hot chow for most breakfasts and dinners. If you can, poop in the mornings when the port-a-potties are the coolest and thus the least "ripe." The port-a-potties near the front gate are less disgusting than the ones closer to the tents.
Get all your uniforms and the stuff you need from the packing list before you get here, if possible. It's just one less thing to worry about. Expect an ASU inspection and try to get yourself squared away sooner rather than later.
Make some friends. My platoon got along very well and we had a great time. Some others spent their time back-biting and one-upping each other, or seeing which prior enlisted student leadership could best show the soft direct commissionees what the Real Army is about... LOL... military customs and discipline are good, but it's sad watching the hooah-er-than-thou prior enlisted try to yell at students new to the Army.
If you are a direct commission with no prior service or prior service in another branch, you need to get enrolled in the BOLC Prep course. Your HRC Branch Manager needs to do this, I think. It is a 2 week course prior to BOLC that will get you up to speed before everyone else shows up.
Let me know if you have any specific questions and I'll try to answer them for you.