The word "gravy" deserves the treatment Eskimos give to "snow," needing one hundred terms to do justice to its many variations.
Gravy is that comforting stuff you will ladle over your mashed potatoes this Thanksgiving; the accompaniment to home-fried chicken; the rich juice that cooks out of a ham. Unfortunately, this basic suppertime pleasure mystifies about 50 percent of the cooks in American households, according to a recent survey - a sad state of affairs, as absolutely no substitutes exist for homemade gravy.
If you are among that 50 percent, be not afraid to learn. At worst you'll pour a few cups of broth down the sink if you mess up. At best, people will find your steaming, savory gravy a highlight of the meal. In fact, when there are gravy makings in my house I often eat only potatoes and gravy for dinner.
Ignoring for now the fancy sauces made with a "roux" or with eggs and cream (see Joy of Cooking or another standard cookbook for these methods), I would like to direct you to that most simple, fat-free gravy method - using cornstarch.
Consider the leftover chicken bones, beef trimmings, or vegetable peelings that grace your cutting board. They are treasures. After boiling them to extract their flavor, add salt, a few spices, and a cornstarch/water mixture, and with very little effort you have made a rich-tasting, delicately textured gravy that will moisten and flavor whatever you pour it on - bread stuffing, acorn squash, couscous, etc.
The most important step is creating a rich broth. Do not add too much water when boiling the scraps; usually one cup of water to one cup of bones or vegetable peelings - onion skins, garlic ends, green pepper seeds, broccoli stems - is about right. Most broth needs to simmer at least one hour (cover, so it won't boil away), but vegetable broth takes no more than 10 minutes.