Almost four years ago I quit going to the gym and started working out with nothing other than my own body weight. The exercises I use are really basic, not super innovative, but very effective. For some more advanced exercises you can find aid in household items like chairs and tables. Also you are not bound to any location; you can basically train wherever you want, e.g. at home, in the park, on vacation. Every exercise that I’ll explain can be done in lots of variations, either to stress the muscle differently (e.g. different angle) or to put more force on it. I’ll explain the basic movement first and then the variations to make the exercise easier or harder, and to help make it more exciting. To start I would recommend repeating every exercise in three sets of 8-12 repetitions. If you can’t reach 8, switch to an easier variation. If you can easily do twelve, try to make it harder.