But you would be wrong.
I'm going to let you in on a secret: You don't actually have to do anything to make composting happen. It just happens. All living things turn to compost eventually.
Do you have a pile of yard waste somewhere in your yard? Something that looks a bit like this?
Well, guess what? That's composting. If you move the big stuff off the top, and dig to the bottom of the pile, you will probably discover a nice layer of beautiful compost, just sitting there, waiting to be used.
I "compost" my yard waste simply by moving my brush pile by a few feet each year, and using the lovely soil that accumulated at the bottom of the pile at the previous location.
You might even have a couple of these yard waste bags languishing in a forgotten corner of your yard. I left these ones out in the rain, and when I tried to take them to the curb, the bottoms had gotten too soggy, and they fell right off. Oops.
But, that's okay. Falling apart is part of the composting process. I'm just going to leave these bags here and pretend I meant to do it. In a year or two, the leaves inside will have decomposed and I will have some nice compost to add to my garden.
You could buy a fancy compost bin. I'm saving up for a fancy one, myself. But you don't really need one. This is our compost bin. It's just a big trash can with holes drilled in the bottom and around the bottom edge. (The holes let the microbes in and the excess water out.)
If you get one with a locking lid, you can turn/stir your compost simply by rolling it down the driveway.
Make sure the lid actually locks on, though.
So, what goes in compost? Anything that used to be growing. If you want to use an open system, like the brush pile or the soggy paper bags, you should only add yard waste. If you want to add food scraps, you should have something with a lid, to keep the wildlife out. For normal backyard composting, you should probably stick to fruit and vegetable scraps (and leave meat and dairy composting to the professionals).
How do you compost? Honestly, just put your compostable materials into your compost bin. Don't worry about perfect ratios. Your compost might take a bit longer if you don't get the mix right, but it will still get there eventually. Ideally, you want to balance "greens" (food scraps and fresh plant clippings) with "browns" (dried leaves and twigs). I like to keep a pile of browns beside my compost bin and cover the greens whenever I add them.
Stir or turn your compost once in a while. Then, when your bin is full, set it aside for a few months and start another one to use while the first one finishes the composting process. Your compost is done and ready to use when it smells like soil.