It's all a game. Yell loud (learn to do this from your belly so you don't blow out your vocal chords), follow instructions, move with speed and intensity... yadda yadda yadda. it's all a mind ****, boot is made to break you down and rebuild you, mentally, into how they want you. in enlisted, it's how to follow orders, in OCS, it's how to lead enlisted marines. Simple as that. Just ignore the insults and mental mindfck games the DI's play.
As for physical conditioning, plyometrics are great. Work on your 3mile time, real pullups (not chinups), and crunches.
Most people have problems w/ pullups, do them properly with good form when you're training, that makes the "cheat" way of doing it so much easier. Having a good strong grip will help as well.
Crunches, most people can do 100 of these in 2 min easy, except me. I struggle to get to 70, although I had a 20min runtime, 20 pullups, and first class swim qual. No idea why. But if you have a short torso and long arms, it helps. Once again, train properly, it makes the cheat way much easier.
Running... just run and your time will improve.
However, depending on your MOS, boot is only the start of it. SOI/MCT is the fun part where you get to go on 12mi humps w/ full gear.
Semper Fi