Technically, the only things that goes into a stock are 1) water 2) bones. Apply heat and time, remove bones, boom. Skim the fat if there is any once it's cooled.

If you want to get fancy and make a stock, you can't go very wrong with an onion, a carrot, and some celery. Don't salt the stock unless you're planning to use it right now as is.

I think the usual ratio is 4 quarts water:one chicken carcass:one onion:two carrots:two stalks celery, but broth is forgiving.