Heisig’s RTK is based around mnemonics for learning how to write kanji, so you could start by looking there :)

Problem is I’ve never used mnemonics for Japanese :/

This is just my opinion so feel free to disagree but I think that mnemonics are a waste of time. The way I see it, I think “Why spend my time making mnemonics and them memorizing them, only to memorize the actual content, when I can directly start raw memorizing the material itself”. Either way, if you’re studying and exposing yourself, you will repeatedly see it until you just know it.

Now, I’m not saying that mnemonics didn’t work for anybody – rather any kind of effort that you put into learning will help you in the end. I just prefer to do it through raw memorization.

So sorry, none from me. You can visit kanji.koohi.com like MisterM said if you need mnemonics for kanji. Though I will say, you’re imagination is the limit.

For stuff like the かします = “cash”, I guess I do do that, but I don’t do it “actively” (if you know what I mean). Things like that just sort of pop in to my head, and most of the time they don’t actually make sense. I’m trying to think of an example, but most are so fleeting and nonsensical that they’re I wouldn’t create a list of them and they probably wouldn’t help anyone else – no one else had the thought process/random inspiration that lead to them. My explanation isn’t that clear, but what you gonna do?

運ぶ（はこぶ）[to carry] – はこ is the word for “box”, and “carry” just sorta fits (one of the more logical ones I guess)

履く（はく）[to wear shoes] – for a brief moment I messed up and thought はく meant “box”, which has nothing to do with anything, but it made me remember anyway XD

逃げる（にげる）[to escape, to run away] – にげる sounds like… a certain N-word, which leads me to think of slaves runnning away (it seems I remember the more logical ones a bit better)

比べる（くらべる）[to compare] – sounds a bit like “club”, which has nothing to do with anything

散歩します（さんぽします）[to take a walk] – the way Koichi says it in the audio for the Anki deck I thought was funny :P (I used strange audio (from smart.fm) to remember 丁寧（ていねい）[polite] too haha)

Do you see my point?

Other words, I just remember because I saw them somewhere and they just… stuck, I guess, for whatever reason. I guess I remember where I saw them, the surroundings or how I wrote them at the time, and that helped.

One more example: years ago, when I was a lot younger, I played this Dragon Ball Z fighting game (Budokai) and the announcer said what I heard to be “Hajimarimass!”, which for some reason I still remember after all this time. When I found out it was something like “begin” I was like :D and it stuck.