How to Improve Your Memory

In the 5th century BCE, a Greek named Simonides had to leave a banquet early. After he left, an earthquake destroyed the banquet hall, and everyone there was killed. Although the bodies were unrecognizable in the wreckage, Simonides identified them all because he could remember where everyone had been sitting. His memorization methods have been used by scholars throughout history, and are still popular today.
List Learning Strategies
These strategies tend to be mnemonic - that means that they link the items to be learnt to information that is already firmly in place in the long term memory. Order and images are the two key concepts. Most of us are already aware of some simple mnemonics, and use them from childhood without thinking twice. For example - how do you remember the colours of the rainbow? A lot of people use the mnemonic "Richard of York Gave Battle In Vain", where the first letter of each word reminds them of a colour starting with the same letter. (Red, Orange, Yellow, Green, Blue Indigo, Violet).The very same principles apply to more complex mnemonic systems, like the method used by Simonides, which is called the method of loci, or the Roman room method. You choose a very familiar room, or house, or daily journey, or even your body. You select items of furniture, or landmarks on the journey, or body parts, and train yourself to always pass your loci in the same order. Then you imagine each item on your list at one of your loci. So if you're trying to memorize your shopping list, you could start by imagining a box of eggs by the front door, a milk carton on the hatstand, an orange on the windowsill, and so on.
A similar strategy uses numbers as memory pegs. First you think of an image that you'll always associate with each number, like a pen for 1, a swan neck for 2, snooker balls for 3 etc, then you imagine each item on the list associated with each of your pegs. For example, you could imagine writing on the eggs with the pen, a swan drinking your milk, rolling the orange at the snooker balls etc. In the link method, you imagine a link between each item, like the eggs cracking over the milk, and the milk spilling on the orange. In the story method, you tell a story that links the items in the correct order.
The problem with all these methods is that it can be hard to recall each item without going through the whole list. Most of the methods are also hard to use effectively without lots of training and preliminary memorization. The loci method has the advantage that the room or journey is already very familiar so you don't have to expend any extra effort memorizing it.