Cold composting is the simplest method of all. You add materials to a pile as you have them and let it decompose slowly at ambient temperature, without much turning or management.
How it works
Just keep adding greens and browns over time. Because the pile does not heat up, it breaks down slowly, often taking a year or more, and it will not reliably kill weed seeds or pathogens.
Pros and cons
It requires almost no effort, which is its main appeal. The trade-offs are speed and the need to avoid diseased plants or weeds that have gone to seed. For a faster route, see hot composting.