Cowboy coffee is a form of black art, and getting a good cup of coffee involves any number of chants, prayers, and even a dead chicken, or two.

That is to say, the most obvious feature of Cowboy Coffee is that it is made without a filter. There is no physical barrier between the coffee grounds and your coffee cup. The grounds are boiled while free-floating in the water.

The trick then becomes how to get the coffee away from the grounds. Here is where the black magic comes into play. Sometimes, if you say the right words, you get get the grounds to settle out on their own. You can skim off the top, and carefully avoid pouring off the bottom, and you will get a decent cup, with only a small puddle of grounds in the bottom of the mug.

Some people claim that you throw a raw egg into the mix. The egg binds the grounds as it cooks. I have even heard of using objects like rocks or pebbles to somehow scare the grounds out of suspension.

As I said, it is a black art. On the other hand, most campfire-style coffee pots have a sieve on the spout, which makes some of this moot.

Update - When I was talking about the eggs, I was thinking about an old recipe for coffee that I had seen a magazine once. I found the reference, in a 1971 advertising insert titled "Chuckwagon Cooking from Marlboro Country"

Campfire Coffee -- a dask of salt
   to make it mellow, an egg to make
   it clear.
Heat 2 qts. cold water in large pot.
Mix 1 cup ground coffee with 8 
tsps. egg* and 8 tsps. cold water;
add a dash of salt. Stir in coffee
mixture when the water boils.  Return 
to a boil, stirring occasionally.
Turn off heat and pour in 1/4 cup
cold water; let stand 10 min.
Makes 8 mugs.
*Prepare egg by beating white and
yolk together; store in refrigerator.