Essentially, you can use whatever you want for your stock. The stuff you’d normally discard when cooking – chicken bones, onion peels, carrot trimmings, scallion roots, shiitake mushrooms stems, celery leaves, you get the picture – all can be used for stock. I like to throw my discards into ziplock baggies in the freezer; then, whenever I’ve accumulated a few bags worth, toss them into a pot and cook up a simple stock. You can use other vegetables as well – broccoli, asparagus, cabbage, beets – but bear in mind that these stronger-tasting vegetables will give your stock a very distinct flavor, making it perhaps less versatile than if you stick with the basics.

As for herbs, I keep it simple with just thyme, peppercorns and a bay leaf. You could tie up your herbs in a cheesecloth sachet, if you don’t want to inadvertently skim away the flavorings as you cook, but frankly, I’m lazy, and can’t usually be bothered to go to the trouble.

A few technical tips …
A good stock should be clear and not greasy. The secrets to a clear stock are, fortunately, pretty straightforward:

Should you still end up with a grayish, murky stock, however, don’t despair. In all probability, the stock will still taste fine. Just do your best to pour out the liquid and discard any sediment that settles to the bottom.

Stocking up …
Homemade stock will keep for 3-4 days in the fridge, and 3-4 months in the freezer. I store mine in 2-cup and 1-cup sized deli container portions, which make it easy for me to use as little or as much as I need for a given recipe. If you’re short on freezer space, concentrate your stock by boiling it down after you’ve strained and de-fatted. Freeze the concentrated stock in ice cube trays (once the cubes have formed, pop ‘em out and store in a ziplock bag) and you’ll have handy little shots of stock ready-to-use.