The memory palace is a very ancient technique, which dates from the ancient Greeks and Latins. Orators in the Roman Senate used this technique to remember the concepts they had to develop in public. To be effective, this technique requires that the places in the palace be always the same and always in the same order.
I attended a course in memory technique back in 1985, then I studied these techniques using a self-course with weekly booklets about ten years ago. I always found that “fancy visualization” is my favourite and most effective technique. That is, if you have to remember something, you associate to the concepts to remember a mental image. The image must be strange, because we remember strange things much more than usual things (suppose you see a man in the street with four arms: you’ll never forget him!). You can also remember sequences of words or concepts, creating a chain of strange, fancy images connected each other (a typical exercise is to try to remember 30 random words in sequence). Specialists of this subject say that sex-related images are very powerful for memorizing.
For numbers there are special techniques which transform a given number into a word or a sequence of words, using a convention that correlates numbers with consonants of the alphabet (e. g. 0 –> Z or S; 1 –> D, T; 2 –> N (N has two legs…); 3 –> M (M has three legs…); 4 –> R; 5–> L; 6–> CH (sounds like in channel); 7 –> C, G (sound like in cat or get); 8 –> F, V; 9 –> P, B.). Vowels are not part of the game. So if you want to remember the number 43217, you associate it to RoMaNTiC; and you have to imagine a romantic scene linked to that number (which is may be the code of your credit card); so you imagine a romantic dinner with a nice girl or a nice man, and the credit card flying above you or diving into the glass of champagne…
The most powerful engine for memory is interest. If you are interested in something, you easily remember it. If you are not interested, memorizing it becomes much more difficult.
DISCLAIMER: This is a post in the discussion forums for the course “Learning How to Learn” wrote by one of the learners, Guido Bertolino.