Prep staff in restaurants get their stock pots simmering at the crack of dawn so they'll be ready in time for the evening service. That's because a proper stock takes 3-8 hours of slow, steady simmering (note: they should never come to full rolling boil).
If you boil your stock it will turn cloudy (as seen here) which I don't necessarily mind since I know what I'm using it for, but normally you want a nice clear stock and you get that by slow simmering. Bubbles should barely break the surface. The low simmer doesn't have your whole house steaming up either.
I use leftover chicken carcasses for my chicken stock, toss in veggie scraps and a bouquet garni from the garden and let it simmer away for three hours before straining and storing in heavy gauge Mason jars in the freezer. Great for soups, stews, tagines and pastas.
So I got three gorgeous (albeit cloudy) quarts of chicken stock (broth) from the carcasses of two mere little chicken breasts. They'll be used in a tagine, soup and a pasta dish this week.
CHICKEN BROTH (STOCK)
Carcass of leftover chicken
Bouquet garni (parsley, thyme, bay leaf)
1 stalk Celery (leaves or ends are fine)
Three black peppercorns
Fresh cold water
Simmer for 3-4 hours
Strain before bottling
(You can adjust your seasonings as you see fit, adding in sage, garlic, salt, etc. Once you get into meat stocks you'll want to roast the bones first and extend the simmering time from 5-8 hours depending on what you are making.) Truly, there is nothing that makes you feel more like a real chef than preparing your own stock from scratch, and I guarantee you, meals prepared with homemade stocks and broths are the ones that need less fat for flavor, and inevitably elicit the "wow, you're a great cook" remark. Using stock instead of fats is the key to dieting without loss of flavor.