(A Bit of History According to Strongblade)
It's pretty simple, really. You line up facing each other at a predetermined distance, take careful aim with a specially made pistol, and fire at your opponent, hoping your bullet hits him and causes enough damage to keep him from firing back.
Dueling was a right of the upper classes. In the 18th and 19th centuries, pistols were added to swords as methods of seeking satisfaction for wrongs. Like the swords used in duels, dueling pistols were a status symbol as well as a means to an end of your opponent. The more attractive your pistols, the more distinguished you were considered to be. This was one of the reasons that so many differnt styles of dueling pistol were created. Hundreds of thousands of beautifully styled and carved firearms were stored in noble houses across the world, waiting for the right insult to be levied against the owner or his associates.
Despite the myriad types of dueling pistols made, most had one thing in common: They had long barrels, These long barrels gave the lead shot a longer and straighter launch, allowing for much more accuracy than common flintlock pistols.
The rules governing pistol duels varied from duel to duel. It was the task of the "seconds" (assistants to each of the dueling men or women) to come to an agreement on the how the duel should be carried out. One of the simplest and most common was the alternating duel.
In this type, the parties stood a certain number of paces from one another, each with a pistol in hand. The challenged party would get to go first, so the challenger would turn his body in profile, offering as little target as possible. The challenged party would then fire one shot at his opponent. If the shot missed, or failed to seriously injure his target, then the challenger would get his turn.
If neither party killed or seriously injured his opponent with the first shot, they could continue to a second round, or end the duel, with neither side losing face or honor. In fact, it was somewhat common for opponents to fire their pistols into the ground, or otherwise intentionally miss each other. This was a good way to get out of the duel without looking like a ninny. Of course, you had to hope that your opponent wasn't going to shoot at you after you fired your round into the floor.
The flintlock pistol was the greatest advance in pirating since the wooden leg. Developed in the 1600s, these pistols revolutionized ship-to-ship combat (and on-land raiding). The concept was fairly simple: gunpowder was stuffed into the barrel. A lead ball, usually wrapped in some sort of fabric, was stuffed in. A metal rod (normally embedded in the bottom of the gun's barrel) was removed and used to jam the ball and powder as far back as possible, and as close as possible. A hammer (sometimes called a cock [insert giggles here]) was then pulled back half-way and left that way until the gun was ready to fire. The pistol technically was not meant to fire in this position, although sometimes they were known to go off half-cocked (and yes, that is the origin of that expression). When the gun was ready to be fired, the hammer (or cock, hehehehe) was pulled back all the way and the trigger was squeezed. A the top of the hammer, a piece of flint was held in place by a vice. When the trigger was squeezed, the hammer was released and the flint struck a metal plate known as a frizzen. A spark would be created, which would light the powder in the barrel, which in turn would make a satisfying "boom" sound. A by-product of this "boom" was the ejection of the lead ball from the barrel at a high rate of speed. Flintlock owners had to be careful that the barrel was not facing anyone when they created their "boom" sound or injury or death could result.
Moisture or water was one of the greatest threats to flintlock pistols. Wet powder would not light when sparked, so the flintlock owner would neither get the satisfying "boom" nor the lethal projectile flying from their barrel. Instead, this would often mean that they, themselves, would be the target of an opponent's satisfying boom and resultant projectile. That, or a sword through the esophagus.
Inspired by Model SBC-FL-FRENCHDUELING-BRASS