Making homemade broth has a reputation for being a long and difficult process. This is true for meat broths, as it takes a lot of time for the collagen and other proteins to break down. You don't have to worry about this in vegetable broth, and you only need to simmer for about an hour. By making your own, you can control the flavors, the amount of salt, and whether the ingredients are organic.
The way I do it takes a little of foresight - saving vegetable scraps in a bag in the freezer. Onion bits, mushroom stems, pepper tops, asparagus ends, all go into the bag to be used when it fills up.
Throw it in a big pot and boil, then simmer for about an hour. That's it!