Disclaimer: Don’t do anything stupid or illegal. It’s bad. Besides, if you’re reading this, you’re just starting out. Locks are cheap, and I really prefer to practice on my locks while sitting around my place with beer, wine or a cigar. Only practice on your own locks. It’s a lot more convenient and locks aren’t that expensive. Ask people for old locks they lost the keys to, or ones that use combos they forgot. Snag misc keys the same way. Trust me, they’ll be happy to fork over the worthless junk cluttering up their storage space.
Like most geeks, back in high school I was always poking at stuff to learn about this whole new world thing. Three things caught my attention: computers, locks and books. I was probably one of the few kids to ever get in trouble on a regular basis for reading during class. I’d finish the textbook in a couple days (and generate solutions for all of the problems, early brute forcing skillz) and move onto whatever interested me. My parents were never quite sure if they should be happy or upset at that discipline issue. Anyways, something that caught my eye were the dinky cheap Master locks that everyone was mandated to buy. I noticed that if a student forgot a combination, the facilities folks never cut the padlock off but used a master key to open any lock. That interested and annoyed me. First off, I didn’t like the fact that anyone could open my locker without my knowing, and second, I wanted to know how to that. I “lost” my padlock a couple times, forcing my parents to buy me new ones. (I was a sneaky devil of a child, if you can’t tell.) I disassembled a couple and the rest I experimented on.
Through my experiments, I was horrified to learn the secrets of the padlock. It was… bad. I learned that it’s called a “warded lock”. The lock employs obstructions to block a key. If you get by these obstructions, you open the lock. Snagging a ton of keys from students at the end of the year, I experimented in mutilating the keys to avoid these obstructions. I ended up making my own “master key” that had all bumps shaved down but one. And it opened any Master lock. Now, you can buy “warded key sets” or “warded picks” online for $10. It’s a set of five types of “master keys” that open nearly any warded lock. Horrible friggin security, but they’re cheap and keep honest people honest.
A master key wasn’t very exciting to the average 15 year old. It doesn’t have good presentation value to the ladies and the only slightly more appreciation among the crowd of my peers. So I wanted to find other ways to pick a padlock that looked more difficult and impressive. Eventually I found a way to make a lock think it should be open. I cut up a soda can, forming an M the size of a nickel. I bent the two side pieces back to re-enforce the ‘handle’ and would slip it into the crack between the shackle and the body of the lock. It’d touch the latch holding the shackle closed and spring it open. This is called “shimming”, with the devices called “shims”. Sweet, we’re lockpicking like the movies now!
Pretty impressive, but not good enough. I did some research and found a program for the TI-81 calculator. You’d clear the lock by spinning the dial a bunch of times. Pull on the shackle, it’d bind up on one of the digits. I don’t recall the reset, but I’d punch them into the calculator and it’d give me a list of ten combos. Could be the first, could be the last. So I practiced quite a bit at entering combos. I finally had an impressive (to 15 year olds) act to crack the locks that wasn’t too easy, but not too hard. I got pretty good at the most inefficient means of cracking a Master lock.
Next up, I wanted to learn how most doors worked. Again, easiest way to figure something out when you’re an impatient kid, bash it open with something heavy and figure out how the pieces go together. Come to think of it, that’s still my primary engineering strategy… So I got some door knobs, bashed them open and studied the components. Significantly, significantly different. Much better design. Much harder to crack but shimming still works. Folks think a credit card is handy, but you want something a bit more flexible. Blockbuster card works pretty well, and they’re generally nice about replacing them after you mutilated it. Or you can buy overly expensive flexible metal gizmo’s to do the same task. Whatever works.
Nearly all door locks are pin tumbler locks. You have a cylinder with an opening for the key that rotates to open the lock. Internally, there are a row of pin tumblers. These pins are on springs, and they prevent the cylinder from rotating. They’re usually of different lengths (hence why your keys have all those bumps). Push the pins up a specific amount, and the cylinder freely rotates. These locks can primarily be picked because the pins are of slightly different sizes and tolerances. The lockpicking is essentially turning the cylinder so the pins are jammed between the cylinder and the rest of the assembly. One pin is binding more than the rest. Push that one up, and now it can’t go back down. Find the next pin offering the most resistance, and so forth.
Enough with the boring exposition. Now, onto the exciting part. Let’s pick a lock.
First, what you need to pick a lock. Locate the following.

You need a lock, a multi-tool (buy a decent one), and two paper clips. That’s it. No, seriously.
Find or buy a doorknob. Any will do. Find the nearly cheapest door lock you can find. Unlock it. Look for a hole between the door knob and the part normally touching the door. Move it around until the holes line up. Stick a small screw driver in it. Wiggle around. The doorknob should come off. Now, there should be a notch in the back of the door knob. Stick your screw driver in it, and wiggle off the ring on the back of the doorknob. Now wiggle out the lock cylinder out of the doorknob. Ta’dah!
The lock assembly you are now holding in your hands is a pin tumbler lock, with between five and seven tumblers. That’s a lot for someone just starting out. There should be a block sticking out of the cylinder shaped thing. On top of that block should be a metal cover. We want to remove it. Break out your trusty multi-tool or pliers. Remove the cover. If there are indentations in the top (most likely), you need to pry perpendicular to the angle of that the key is inserted. Watch out, the springs may shoot out. Once you remove the cover plate, use your multi-tool to crush the indentations to being level with the rest of the plate. Now, dump out the contents of the lock. You should get five or six springs, and twice that number of brass pins. One set will be virtually identical. The rest will be slightly longer or shorter. Take ONE of the brass pins from that are virtually identical and drop that one in the first hole closet to the key hole, then drop in one of the variable length brass pins and lastly drop in a spring. Now, slide the cover plate back on. Use your multi-tool to crimp it back into proper shape, but being relatively easy to slide on and off.
We now have a one tumbler lock.
Take two paper clips. Nice mid-sized metal ones. Straight one out into a line, then hold one end into a handle. The other, take the middle loop of metal and bend it out until it is perpendicular to the larger loop, forming an L. Crush the inner loop slightly with your multi-tool. Insert the smaller loop end of the L into the bottom of the lock, away from the pins. Congratulations, you have just made your first lock-pick. It’s a torsion wrench (most often incorrectly called a tension wrench). Your straight line with a handle paper clip is now a “pick”.
Play around with your torsion wrench. You want to make it stick out at a comfy angle. Push on it just slightly with a finger, preferably the same one holding the cylinder. It should also be out of the way so you can freely move your pick.
Here is a way of holding the cylinder and torsion wrench.

And another.

Now, put your lock-pick in the keyhole and probe around inside the lock. Get a feel for the inner dimensions of the lock, without all the pins in it. After you get a feel for the dimensions of the lock, find the tumbler. Put a slight amount of torque/pressure on the torsion wrench and slowly push the pin up. You’ll have to play around a bit with how much torque you’re putting on the lock. You shouldn’t need a lot. You might have to work the pin a few times. When it gets to the right spot, the lock will freely turn. Congratulation, you picked your first lock.
Remove the cover plate from the top of the lock, move the tumbler to another hole. Repeat a bunch of times. It should be pretty easy after the first few tries. Now, let’s make things more complicated. Toss in TWO tumblers. After you apply torque and you start probing the tumblers, you should notice one of the tumblers offers noticeably more resistance. That’s the tumbler with the pin that is binding. Press that tumbler up first. Then press the looser tumbler up secondly. It may now offer more resistance than the previous time you pushed on it, as it’s now the pin that is binding.
Stick with the two tumblers for a while. Move them around between the different openings. After you’re really comfortable, you can start adding more tumblers.
If you’d like an unsolicited suggestion. Don’t buy a “lock picking set”. They’re really overpriced and include lots of stuff you don’t need. Buy a torsion wrench (aka a tension wrench) and a half-diamond pick from any locksmith supply company on the internet. They should be a couple of bucks each. Don’t pay more than roughly $5 for either. You might want to consider buying a couple different variations of the tension wrench and half-diamond pick. You can buy nicer picks later if you really like lockpicking.