Essentially, it involves taking information, converting it into an image, and storing that image, usually in a linear manner, in a well-known place in your mind.
But what if you don't need a list? What if you need immediate access to information, but don't know exactly which piece?
Restated for you computer scientists out there - What if you don't want a linked list? What if you want an array? What you need is instant access to any one item, not the ability to iterate through many items.
Introducing... (funny trumpet noise) ...the Pegboard.
A pegboard is a method of linking pieces of information without the need to spacially locate images. The trade-off is that your images typically need to be WAY more ridiculous than they usually are, as the association is the only thing keeping it stuck in your brain.
Okay, but how does it work?
I'm glad you asked, well-timed bold font.
Let's say you want to be able to remember 3 things. We don't know what they are yet, we just know how many there will be. Let's start by creating some pegs.
Peg #1, where we will hang our first memory, will take the form of a GIANT foam finger, the kind you see at sporting events.
Peg #2 will be poop. That's right, poop. A deuce. Number two.
Peg #3 shall henceforth be a large tree. It can be any tree you want, so long as you can see it in your mind.
It's important to note here that there's no reason your pegs need to be these images. Anything that provides a reliable association with the numbers will work great.
Now that we have our pegs, let's try remembering some stuff. The first item we will attempt to memorize is a bright green plastic drinking-straw. In order to lock this into our pegboard, we simply combine it with the image for peg #1. For example, I imagined an angry fan getting his coffee spilled at a football game and, as revenge, stabbing the straw through the massive foam finger held by the man who bumped him. Now the straw is poking through the foam finger and maybe even whistling in the breeze a bit.
The next item we need to remember is a leather briefcase. The scene that pops into my head is one of a snobbish businessman brushing past me on the way to the elevator because he believes that his time is much more important. However, I have acted quickly and have switched his case for an identical one filled with excrement. Just as the elevator doors close, I see the case pop open. The contents spill out and the man is forced to ride up the elevator with a small crowd of people who believe he brings his poop to work.
I'll leave you to come up with a funny story that explains how item #3, a grand piano, came to be involved with peg #3, a tree. I'm sure it will be wonderful.
Now, in order to recall the memorized items, we simply need to recall the peg they were stored on, and the ridiculous story we have created will shoot back into the forefront of our mind, filling in the missing information.
Example:
"Oh I sure do wish I could recall what item #2 was. I know that peg 2's image was poop, but past that, I'm not sure....
Oh! That's right! I put poop in the businessman's leather briefcase!"
(Giggling fit ensues)
This technique can be expanded almost infinitely, as it is limited only by the number of pegs you create for yourself. In addition, the pegs themselves do not need to be numbers. They could be letters of the alphabet, names of people on mail slots, evidence tags, etc. Any data that needs to be linked to other information you don't know yet can serve as a peg in a pegboard.
Here's a link to a Wikipedia page on pegboards for further reading.
They go through a slightly longer example, and touch on some of the ideas behind actually choosing peg images, like rhymes.
Happy memorizing!