1. First, bend the paper clips into a tension wrench and a pick. The first paper clip, the "pick," should be unbent so that it's completely straight.
2. Make a tension wrench by opening up one end of the second paper clip into an "L" shape.
3. Put the tension wrench paper clip into the bottom of the keyhole and push it in.
4. Now, insert the pick into the top of the keyhole, called the shear line. The shear line is made up of pins that match up to the low grooves on the key to that lock. Insert the straight paper clip into the top of the keyhole, against the pins in the shear line.
5. When you insert your pick paper clip into the top of the keyhole, you should be able to feel the pins push up as you rake across them. At the same time as you quickly pull the pick paper clip out, raking it upward against the pins, apply slight tension to the end of the tension wrench paper clip. You'll be applying tension either clockwise or counter-clockwise, in the same direction that you usually turn your key in order to open the lock. When the combination of tension you apply to the pick and the tension wrench paper clips is exactly right — voil! The door should be unlocked, and you should be inside enjoying a celebratory beer.
6. Still stranded on the front stoop? Practice makes perfect. It's unlikely you'll get this on the first try, so if you have a habit of forgetting your keys, you may want to get it right before you need to. Your best bet is to practice on a lock inside of your home — trying it out on the front door of your apartment building is likely to alarm the neighbors.