Store your vegetables scraps in a ziplock bag (or other container) in the fridge until you collect a reasonable amount.
Wash the scraps, place in a pot, add water and simmer on medium heat for about 40 minutes, without bringing to a boil.
Use a cloth, paper towel, etc., to strain the broth.
Once cooled, transfer to a container. Put any soup you're not going to use into a freezer safe container and store in the freezer.
Story Behind this Recipe
I thought up a simple and delicious stock recipe.
Any vegetables are fine - daikon radish, carrots, onion peels, spinach and mizuna roots, broccoli stems, the outer leaves of lettuce and cabbage, etc. But try to limit yourself to vegetables only, and avoid using animal proteins. Depending on the kind of vegetable scraps you use the taste of this stock will change, meaning you get to experience a new flavour every time.