Composting

General questions:

Where are you and what's your general environment like? Mostly urban? Suburban development with heavily-fertilized lawns? Gardening? Cook a lot of veggies?

What are you trying to do with compost? Feed a garden? Reduce landfill usage?

What to put in the compost:

Plain grass clippings are great but they don't usually compost all that well by themselves. The standard advice is to mix both "greens" (nitrogen-rich: grass, twigs, paper, corn husks, etc.) and "browns" (carbon-rich: leaves, vegetable & fruit scraps, animal manure) to get composting going.

Kitchen scraps are a great source of "browns" — peels, stems, coffee grounds, tea bags, etc. Pretty much anything from a vegetable source that doesn't have fertile seeds in it, is a good input to basic composting.

(Why do I call out fertile seed? If you throw a whole rotten tomato in the compost, you will get little tomato plants growing in there. Onion & carrot tops can also decide to grow in there, but they give up if you smash them a bit.)

Regarding earthworms:

The kind of earthworms that like to eat compost are not going to just spontaneously show up out of the ground, because the ground is mostly not compost. You can get them from someone else's compost; or they're also commercially available as "red wigglers" or compost worms.

Worm-based composting works pretty differently from straight composting. Some say that "vermicomposting" should really be called "vermidigestion" — it's relying on the digestive tract of the worm, not composting microbes, to break down your veggie garbage.