Chunk up the veggies, don't worry about being too particular on sizing, as they're just going to go into the pot, get cooked down, and then strained out.
Fill a stock pot with water, I go with about 3/4 of the way full, and add more as needed.
Dump all veggies, and which ever protein you're using, in, adding in the salt and pepper.
Simmer stock over medium heat for 12 or so hours, stirring occasionally.
Strain out all solids, I generally pour the broth through a colander into a second stock pot. Make sure that you do this in the sink, as it can get kind of splashy.
Using a ladle, scoop the broth into mason jars, through cheese cloth. Trust me on this one. Not a step you want to skip. Make sure that you leave an inch or so of head room so the jars don't bust as they freeze. Once the broth cools it goes into the freezer and you're all done. Except for washing the stock pots. Not my favorite part.