Red-eyed, lesser CRD
When we say that someone is "at a crossroads", we mean that they have an important, often life-altering, decision to make. The phrase comes from an ancient custom, reaching at least as far back as Babylonian times, of summoning demons to make a pact with them, often at a crossroads. Demon summoning can happen anywhere, at any time, and often involved certain "favors" being done with the demon in order to seal the deal. If a woman did the summoning and had a child out of the act, that child was given over to the demon. In many cases, such as the famous story of Faust, the person did not just make a deal with a demon, but with Satan himself.
Supernatural, surprisingly enough, deals only with the simpler side of the story. To make a deal with a demon, the summoner goes to a crossroads and plants in the center a small box containing graveyard dirt, a black cat's bone, a small flower called yarrow, and- most importantly- a picture of the summoner. Then a red-eyed demon appears in the body of some human. Often men see a beautiful young woman, altho Crowley, the King of the Crossroads, possessed a fat guy with a caustic sense of humor and a Cockney accent.
Usually the demon grants your wish and gives you ten years before a pack of hellhounds attacks you and rips you to shreds, dragging your soul to hell. With some deals, such as bringing someone back from the dead, the time frame may be shorter. Salt works as a deterrent against hellhounds, as does goofer dust (made of graveyard dirt, powdered sulfer, and salt, and sometimes also includes powdered snake's heads, bones, insects, and black or red peppers). However, the deterrent only lasts for so long....
The demons people usually meet are the lesser ones. The highest ranking Crossroads Demon, or CRD, was Lilith, the oldest and first demon who held all the contracts until Sam Winchester killed her. With most CRD's, a kiss is all that's needed to seal the deal. With Lilith, it would take a little bit more.
All deals with demons are binding and unbreakable, unless another deal is made to break it. Even the demons can't weasel their way out; they have to follow the guidelines set in the contract, which is written invisibly under the client's skin. But beware! Binding though the contract may be, demons can include clauses, subclauses, and loopholes in the fine writing, which is found somewhere on the lower abdomen. Crowley was especially good at this.
Good thing to remember: It's unseemly to make deals with demons.
Crowley's first appearance