The hardest events at boot camp are the conditioning marches just because of the physical discomfort of carrying a light pack. It’s just because you aren’t used to carrying anything for an extended period of time that you won’t be used to it… the loads aren’t really that heavy only 40-50 lbs at the most.
I would reccomend the Recon Ron Pullup Program to build up your pullups strength thats the program I used when I was preparing for boot camp and I have no trouble getting 20 pullups anymore… in fact on my final PFT at SOI I did 25 because I did an extra on for “Myself, the Corps, Chesty Puller, OIF, and OEF” according to my Combat Instructor… haha
To build your situps I would reccomend a simple circuit of the following to start off with: 20x standard situps, 20x crunches, 20x hanging leg raise, and finally 20x dragon flags (basically toe touches but you crunch up and raise your legs at the same time to touch them in the air)… Other than that simple pyramids help 5, 10, 25, 35, 25, 10, 5 with 30 seconds of rest or something like that… what helped me the most was doing 8 x 25 sets of situps… and then when I built that up I did… 4 x 50 and then 2 x 100. I haven’t really had to work on situps since though because one you have it… its almost like pullups you just don’t lose the skill.
To help with the 3 mile run I recommened a simple running template of Monday, Wednesday, Friday, Sunday running. Monday do speedwork for example: 6 x 400m sprints, Wednesday do a tempo run or fartlek training run at a decent pace for 1 mile, run hard for 2 miles, cool down with 1 mile, Friday I’de recommened actually running a hard 3 mile run at your PFT pace and Sunday I recomend an easy jog for time…
I’m no gifted runner by any means, but I used something simple like this… to accomplish a run time of 20:21.
Concentrate mainly on your pullups and situps though… they are easy points. As you become more proficient at each exercise scale the workouts… add pullups, crunches or distance/time to them so they increase in difficulty as your fitness gets better.