If I have a jump rope and a resistance band, I can work out anywhere. Even without a jump rope. If you do 200 jumping jacks, then drop and do some crunches, and then do some squats, you're good.
I lift weights. I'll do a lot of running, a lot of cardio and strengthening. I use my body weight, a TRX sometimes. A lot of it is endurance.
There's so much you can do with bodyweight alone. The basics always come up for a reason: sit-ups, planks, push-ups. They'll always give you results. The way to take it up a notch is to compound the basics to work multiple muscle groups at once.
I've got this old-school workout - push-ups, sit-ups, tricep dips. And it worked. Anybody can do this at home.
I like to use the world as my gym. I walk around and if I see a stairwell I might do a couple of dips on the stairs.
My system uses no apparatus. The resistance of your own body is the best and safest apparatus.
Sit-ups and push-ups work without a gym.
I've always needed to bulk up, so until the modeling took off I was ramming Big Macs down my throat and doing plenty of bodyweight work. I'm over the Big Macs now, but I'll still drop down and do my press ups whenever I find the time.
An ordinary pushup is much more advanced and challenging performed on a stability ball.
Burpees are great, but they just kill you.
You can't read about push ups. You gotta do them.
Even if you can't do a full real push-up, I'd rather have you do them with a limited range of motion and work up to the perfect pushup then do them on your knees, where you probably won't progress at the rate that you could.
I think squats is a generic thing - you can do squats with anything. That's the great thing about it. As long as you get in a safe position to do it.