It all starts with the most basic thing of all: water. Then you start tossing things into it. If you need a primer on the concept, I highly recommend you read the folk tale Stone Soup (the version Captain Kangaroo read to us in the good old days). I have it on good authority, though, that there is such a thing as throwing too many things in a pot. A basic vegetable stock is still rather difficult to destroy (IMHO, one guaranteed method is to include Brussels sprouts, rutabagas , or turnips, but that's just one cook's attitude). Oh, also, try to use real, rich carrots, not those baby-type things, as the finger food ones have too little flavor for anything other than absent-minded noshing.
1 gallon water (approximately)
1-2 tsp olive oil
1 large sweet onion, chopped (about 1 1/2 cups)
1 large red or yellow bell pepper, chopped
1/2 medium green pepper, chopped
2 cups celery (including leafy greens), chopped
1 cup carrots, sliced no thicker than 1/2 cm. (you can grate them if you prefer)
1/2 cup chopped cabbage
1 cup corn, frozen or fresh from cob (NEVER from a can!)
2 cloves garlic
1/2 tsp fresh grated ginger
3 bay leaves
1/2 tsp lemon zest
1-2 tsp sea salt
1/2 tsp finely-ground white pepper (you can use black pepper if it's what you have on hand)
1/4 tsp paprika
In large stock pot, bring water to simmer. Add all other ingredients, bring heat back up until simmering again, cover, continue to simmer for a few hours, until the liquid has reduced noticeably. Remove from heat. Strain out the veggies (you can save these to toss into a meatloaf, later, if you want... or they still make good compost).
Serve with chopped scallions or chives as garnish, or set aside to use in other recipes.
This can be frozen for quite some time.