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.
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 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.
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.
An ordinary pushup is much more advanced and challenging performed on a stability ball.
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.
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.