The only problem is that many characters with the same ON reading have very little to do with one another. They bear no resemblance strong enough that they could easily be grouped together and remembered. This is what KanjiTown is for.
Basically, KanjiTown is a catchy way to say "Group characters based on ON reading, then think of a unique location to correspond with each group." Locations can be real (Your high-school math room) or imagined (A dungeon in The Legend of Zelda). Recently I googled KanjiTown to find someone that took the same method but instead of using locations used different MOVIES for different kanji groups. What a good idea! If you are a gamer, I imagine you could have different GAMES correspond to different kanji groups. Or if you are a literature nut, different BOOKS could be used for the different groups.
I found that using this method of grouping kanji was my other "secret weapon" for Japanese fluency (Supermemo being the first one). When I saw a kanji, the ON reading seemed to "jump" out in my mind. Not only did I recall the reading and meaning quickly, but reading Japanese felt like reading quotes from my favorite movies and TV shows ("Oh, I remember when such-and-such character did such-and-such-action, that was awesome!). Also when I hear a word I don't know, it is surprisingly easy to correctly guess what the word is based on the hints provided by the pronunciation. The more you do this, the better you get at guessing.
Because of Supermemo and KanjiTown, Japanese no longer requires a significant amount of time to study (Aside from review in Supermemo). I spend a minimal amount of time every week finding Japanese words I don't know and putting them into Supermemo (I'm trying to learn slang words, internet terms ("2828" is ツンデレ, for example) and onomatopoeic words to spice things up). Nearly all of the terms are learned and retained with very little effort (Thanks Supermemo!). If learning Japanese is an MMORPG, now I am in the "endgame" phase now.
Please don't get the impression that I'm bragging. This is simply the result of the methodical application of useful tools. I am convinced that if others used the same tools (With effort, of course), the same result could be achieved.
The reason I post this is because I've struggled to put together a similarly useful system for recalling the pronunciation of Chinese characters. Based on how well the Japanese system has worked, I knew that a Chinese system was possible, but I wasn't sure how to do it. To make a long story short, I recently "cracked" the mnemonic "code" to make such a system work for Chinese, but before I went "gung-ho" into remembering Chinese I wanted to do a thorough check to make sure all of the Japanese kanji were properly "archived" in Supermemo (Both the meaning and the pronunciation of the character). Before I started another big project I wanted to make sure the first one was done.
Tonight I finally finished this project, and I can say with confidence that all of the kanji I studied are in the hands of Supermemo, never to be forgotten (Or at least 90% of them).
Next post: How to beat the crap out of Chinese vocabulary acquisition.
(Just to clarify, KanjiTown is purely for vocabulary purposes. Grammar is a separate beast. )