This is really a good method for opening doors that are locked. The only problem with this, though, is that it only works for outward opening doors.
Ok, here we go....

1. Realize you are not working with the actual lock, but that thing that sticks between the door and the wall.
2. See how that thing is curved on one side? Well, that is what we will be making use of.
3. Acquire a large paper-clip. If it is too short, it won't work. You have to also have a shoelace. Now, onto the construction...
4. Straighten the paper-clip.
5. Loop one end of the paper clip around the shoelace. The shoelace should be about 4/5 on one side of the clip and 1/5 on the other. Let's see if I can draw it.
6. All you have to do now is curve the paper clip (no, I won't draw it)
7. With the curved paper-clip, stick it between the door and the wall, behind the metal thing that sticks between.
8. Feed it through with you hand, until you can grip both sides of the shoelace.
9. Now, simply pull the lace and the door at the same time, and TAdaaaa..the door is open.

I prefer this over regular lock-picking if the door opens outward, because it is a lot quicker. Lock picking can take 5 minutes... When done correctly this only takes 30 seconds! So, if you can, use this. another addition to the mighty cookbook