Check out books of the memory champions (Tony Buzan, Domnic O'Brian, Joshua Foer). The idea is not to improve your memory, just to use it efficiently. The core

Check out books of the memory champions (Tony Buzan, Domnic O'Brian, Joshua Foer). The idea is not to improve your memory, just to use it efficiently. The core is very simple: our brains have a hard time memorising abstract things. Solution—convert them to highly vivid imagery/stories. Visualisation being step one, step two is somehow to link the resulting images. Here you have a choice of link system, peg system, memory palace/method of loci. That's basically it. You will probably learn some system for converting numbers to images (Major system, o Dominic system), but that's just a tool for the first step. Also, get enough sleep.