I have two main techniques to remember things (I'll put them in separate posts as I don't have the time to do them both now)
The first is called the peg system, and is used for remembering numbers: whether it be PINs, phone numbers, or just a random string of numbers.
What the peg system does is convert numbers into letters, letters into words, and if needed, words into stories.
Here are what letters I change the numbers to:
1-l (they look similar)
2-n (an n has two
3-m (an m has three
5-f or v ('f'
e: again, they're similar sounds)
6-b/p (b looks similar to 6, and b and p look and sound similar)
7-T (look similar)
8-ch/sh/j (because of the 'gh' in eight, and then 'j' is close to these sounds)
9-g (again, a g can resemble a 9)
0-s/z ('z' in zero, while the s sounds similar)
I know that may be a lot to learn, but unfortunately you just need to know it. You may also find different versions online - such as the 1 being a t, or the 6 being a g - but this version has worked the best for me.
Now, lets put it into practice. Lets say your PIN is 2137, in the peg system that becomes NLMT. However that doesn't help, now it's just random letters instead. However, if you split it up, and add in some extra letters (preferably letters which have not been used yet, to avoid confusion), it becomes NaiL MaT. Then you can imagine that the bristles have been replaced with rusty old nails
on your door mat
, preventing you from entering your house. Make this picture really vivid: the funnier, the uglier, the more disgusting, the more repulsive the image, the more memorable it will become.
As I said this can work with any number, no matter how long. If a number is quite long, then convert it into words and create a ridiculous story, incorporating those words. I also find it works well if you break the numbers/letters into groups of 2s or 3s as it makes it easier to make words
You may also just need words for single letters, so here are the words I use:
4-door (I tend to use another word which rhymes with four, but thought it best if I didn't say it directly)
Give it a shot, you'll be surprised by how easily you'll be able to recall these numbers. If you get stuck on any numbers in particular, just ask and I'll tell you what I use. Good luck