This skill seems simple, but there's more to it than meets the eye...
In the following video Climbing magazine's Julie Ellison discusses how to appropriately clip the rope into a draw and explains some of the dangers that you should be aware of while clipping.
There are a couple of things in this video that Julie discusses quite quickly. Following is some additional information on these topics.
Carabiners Oriented in the Same Direction:
A quickdraw should aways be clipped away from the direction of the climb. In other words, both the gate on the bolt and the gate on the bottom carabiner should be oriented away from where you are actually climbing. If you are clipping to the right of your body and will be climbing up left, then the gates should face right. If you are clipping left of your body and you are climbing up right, then the gates should be facing left.
Occasionally, you can't tell where the climb is going. In these cases, you just have to make your best guess.
There are two reasons for why we orient the gates away from the climb.
First, we want the rope to run over the spine of the bottom carabiner. This will keep the rope from accidently coming unclipped in the event of a fall. Occasionally, the rope will run over the gate perfectly during a fall and become unclipped, which could have catastrophic consequences.
Second, there have been occasions when the carabiner on the bolt has become unclipped. While rare, orienting the carabiner away from the line of the climb decreases the likelihood of this happening. If you poke around online, you'll find several of occasions where this has happened.
Loose Carabiner and Carabiner in Rubber Gasket:
The loose carabiner should always be on the side that you intend to clip to the bolt. The carabiner in the tight side of the draw should always be the carabiner you clip your rope to.
It's not a bad idea to use the same carabiners every time in the same positions. Carabiners that are bolt carabiners develop tiny groves and inconsistencies in the metal. These can damage your rope.
Carabiners that are rope carabiners are in the tight spot so that it's easier to clip them. The lack of rotation in the draw makes it easier to clip while at a funky stance.
A Final Note On Clipping:
Julie describes two orientations from which you clip carabiners. It's not a bad idea to practice both clipping styles when you're on the ground. This is the type of skill that you can do over and over again while watching tv. Clipping quickly and effectively should be second nature...
--Jason D. Martin