Lock picking is done with two tools, a tension wrench and a pick. Though far from ideal, in a pinch these can both be crudely fashioned from a single paperclip. Though the process is simple and the materials easy to find, picking a padlock with a paperclip can still be challenging for a beginner. With practice, however, it's possible to get a feel for lock picking, and then popping a low quality lock with a paperclip becomes quite easy.
Break the paperclip. Unfold the paperclip with a single bend so it is in an "S" shape. Break the clip in the center by bending back and forth repeatedly. The result will be two looped pieces, each with a small hook on one end where the break occurred. Unfold the two separated piece into "L" shapes, so they can be used as the classic pick and torsion wrench tools.
Apply pressure with the "wrench." One of the two "L" shapes can be used as a torsion wrench by inserting the hooked end of it about a 1/2-inch into the bottom of the keyhole. Turn the wrench clockwise, applying pressure to the lock plug, the part that contains the shaft for the key, and creating a lip where the pins can rest without blocking its movement.
Start picking. Insert the straight, unhooked end of the other "L" shape into the center of the keyhole right where the rounded bend of the key would be. This will act as a pick to lift the pins of the lock out of place. Quickly jiggle the pick up and down, keeping it in the center of the keyhole, and rake it against the pins. Be careful not to bend the paperclip pieces, but maintain clockwise and downward pressure on the lock with the wrench.
Pop the lock. If done correctly, the lock's pins will be displaced by the pick and come to rest on the slightly turned plug of the lock. The clockwise pressure on the wrench will turn the keyhole and pop open the lock.
If the keyhole is too small, use the straight, unhooked end of the wrench to create extra space.
Paperclip tools will only be strong enough to pick locks of inferior manufacture. More sophisticated locks, or those made of heavier material, will require more professional tools and techniques. Though picking a padlock shouldn't damage the lock, it is possible to render the lock unusable. Never pick a lock you don't own or have permission to pick, as this can be illegal.