3-4 carrots, coarsley chopped
2 red or green bell peppers, coarsely chopped
2 large yellow onions, coarsely chopped
3-4 celery stalks, coarsely chopped
4-6 whole garlic cloves, cut in half
1 small bunch parsley, stems and all, chopped
1 bunch broccoli, coarsley chopped (optional)
6 or more cups water (enough to cover all the veggies)
1/4 cup dry white or red wine (optional)
Any other stems, trimmings or leftovers from greens or vegetables you are using.
Combine all the ingredients in a large stock pot, make sure all the vegetables are covered with water. Bring to a simmer, cover, and cook for 4 hours at least (7-8 hours is preferable for a rich stock). Add more water to the pot if necessary to keep the vegetables covered with liquid.
After you are finished simmering the stock, use a strainer to strain out the vegetables, and save the liquid (obviously). Your stock should last a week or more in your refrigerator, or indefinitely if frozen.
Casual Kitchen: How to Make a Versatile Vegetable Stock