My wisdom on gravy:

I learned how to cook from someone who grew up in the south, and as such, I know more about grits, gravy and mayonaise than anyone else in the state of California...

But how to make gravy - making any kind of gravy is a two part process

part 1:
You heat up a pan, preferably something that holds a lot of heat, like cast iron. Put in some oil or butter or margarine, let it melt/heat. (I usually add a secret ingredient at this point - caraway. Its a common meat flavoring, and the hot oil draws out the flavor) Add flour (after the oil is hot) until you have a bubbling viscus paste. (soft enough that it will still run, but enough flour to sop up all the oil). The more you let the flour brown, the darker the gravy will be, and the toastier the flavor, but the less the flour will thicken, and you have to stir it constantly. Let's face it though, making gravy is really all about the art of stirring.

Warning: the more paste you make, the more gravy you will have, it goes a long way. I would start out with 2-3 tbsps of oil. I inevitably end up making about 4 cups of gravy, which is way more than two people will ever eat.

Part 2:
You add your liquids to it, stirring like mad with a whisk to keep it from getting lumpy (or to disperse the lumps as quickly as possible). It should thicken as it cooks. The liquid to paste ratio determines how thick it will be. According to my sources, lumps are a sign of failure, but in my world, its just another excuse to whip out the blender. What liquids? Well, that is the part where the nutritional yeast comes in. I usually make up a pint glass (3/4 of the way full) of:

-milk (soy, whatev)
-diced fresh herbs (whatever i'm in the mood for: basil, thyme rosemary parsley. I like little bits of green tasty stuff in my gravy...)
-dehydrated onion and garlic
-veggie soup base
-nutritional yeast (this is totally an acquired taste, I usually add several tablespoons, but if you don't cook with it much, you might want to start out with less...)
-dash of terriyaki sauce
-and if i'm feeling really decadent I'll carmelize some onions and throw them in there too.

I usually make up slightly less liquid than I think I need and then stand there with the milk carton and add a few drops as it thickens until I get the perfect consisitancy.

this is the recipe I use every thanksgiving...

i sneak in a handful of sliced, satueeed mushrooms, and onions, as my mom used to make gravy with giblets...