All types of stuff. If your making a compost pile, make sure you stir it every once in a while, it will help break it down. I have eggshells, strawberries, leaves, lawn clippings, saw dust, bannana peals. Can't remember everything
You can take like a sheet and put it underneath the soil at different levels. So like soil/newspaper/soil/newspaper. and when it breaks down it is suppose to be good.
Youll have to really do some research if you want to do your own composting don't just throw your scraps in a pot and call it soil, composting takes time and care.