What do I need to do to get ready for Army Infantry?

I had a bunch of comical suggestions but I think I will save them for now. From when my son went to basic over a year ago all i did was run, do some pushups and sit ups with him and take some nice nature walks with a minimal weight in them with him to give him a taste, I think 35-50 lbs. The best advice I can give you is not to injure yourself before attending OSUT at Ft. Benning. Injuring yourself by trying to become a Delta Operator before you attend OSUT is a recipe to be medically discharged. Learn to listen to your DI's even if spittle is flying from their lips. It is a special ability to really listen and absorb information without running your mouth because you are angry or upset. Stay in the middle of the herd or just to the front of the middle. You will have plenty of time to rise above your peers and show your metal when you are not in a training environment. Don't stick out for bad reasons, attitude, personal Hygiene, equipment SOP's etc. Once you get your cord you will report to your unit and the education will continue until your last day in uniform. Watch out for Buddy Phuckers, don't loan money to friends who you will then lose as friends. Always be early to formations, meetings and classes. Give it your very best 24 x 7 x 365 and become a team player. Look out for your buddies and have them look out for you. When you screw up, own it, no excuses, no dissertations as to why your really were not in the wrong because responsibility is the building block for leadership. But above all, "ALWAYS" do the difficult "RIGHT" against the easy" WRONG". Look for good leadership all around you and adapt into your abilities for the future should you become an NCO/OFFICER. Just as important observe "TOXIC/WEAK" leadership and do your best not to add that to your leadership style. Good luck and in 20-35 years you to will sound like a box of Rice Krispies as you get out of bed in the morning :)

How are you physically?

Getting in the best physical condition you can helps. Be balanced in a more cross fit way. Mental attitude is huge. Be prepared to be put under stress. It's part of the process of making you an infantryman. Listen and learn. As much as you think you might know, you don't.