I’m afraid not – I don’t have a reliable system. But very much emphasise with the ineffectiveness of using anything like the visualisation/memory tricks you see people doing on TV/in books etc.
However, autism has gifted me with an excellent long term thing for some things (but not others – and I have little control over what sticks) but a poor short-term/working memory…which presents a combined interesting set of challenges! What I have found helps with memory is effectively practical use/memory muscle but it has to be tangle – so writing/typing/seeing in the real world…it doesn’t work with just repeating in head.
I struggle even with remembering six digits; it only works if I break up into memorable 2 x 3 or 3 x 2 patterns (really annoying in a world of mass conference calls). I’ll remember those eventually I use twice a day but not a ‘new number’ I might only use once a week. But, 25 years later I can still remember the odds of winning a six ball lottery draw using 1 – 49 (GCSE coursework subject in mid 90s…) – 13,983,816 *sighs*