(Note: If you are limiting excitotoxins in your diet, this is not a safe recipe as cooking meat and bones for long periods of time tends to release/create excitotoxins.)
Bone broth is really easy to make. All you need is some bones, a big pot, and some water. I like to cut the meat off the bones and save up my bones in a bag in the freezer until I have enough to make broth. I usually use about a quart of bones, but the amount doesn't matter.
Put the bones in the pot and add enough water to cover the bones by at least an inch or two. Add a tablespoon or two of any edible acid--I usually use lemon juice, but a lot of people like to use apple cider vinegar. This can be left out if desired, but the acid helps to draw the minerals out of the bones.
Bring to a boil, turn down to a simmer and cook for a very long time. I usually cook mine for 24 hours or so. Replenish the water as needed to keep the bones covered. I usually leave a lid on for most of the cooking and then take it off at the end to condense the broth. Cook the broth until the bones start to get soft and crumbly--the idea is to get as many minerals as possible out of the bones. You can add spices, vegetables and/or salt during the last part of cooking if desired.
If desired, remove the bones and simmer, uncovered, for several more hours to condense the broth to just a few inches in the bottom of the pan (usually half the original volume or less). This will make it concentrated enough to freeze in ice cube trays to use like bullion in recipes.
You can use bone broth as the base for a soup, add it to casseroles or other dishes, drink it plain, or use it however you wish. It's chock-full of calcium and other important minerals.