Well, as far as BMRs to get into Basic in the Army, the physical standards go like this:
13 Push-ups in one minute
17 Sit-ups in one minute
1 mile in 8 minutes, 30 seconds
There's some basic drill, land nav and miltiary knowledge requirements before you're decided 'good to go,' but I haven't reached that point so I don't know what they do if you don't make it. Real simple stuff.
And for people in DEP under the Army, there's a correspondance course offered for DEP soldiers which will get you promoted up to PFC (E-3) from the start. The course is optional, and consists of land nav, combat lifesaving, effective writing and communication, and the like. I'm working on the land nav portion right now, and it's very in-depth. But that extra jump in pay (start out at $1,450 a month base pay versus $1,050-odd) is worth a little extra brain sweat for learning stuff you'll need to know in Basic anyways.
Hope this helped.