I APOLOGIZE IN ADVANCE FOR ARGUING ABOUT THE MERITS OF THE HEISIG METHOD. I WROTE THE ENTIRE POST WITHOUT REALIZING WHAT I WAS DOING.
I
didn't use the Heisig method but now that I've been studying Japanese for a long time, I can really see the value in it. Kanji has a way of simultaneously fostering and impeding the development of vocabulary: when you know the kanji involved, everything is dandy and the words are in fact easier to learn because the language has a memory tool built into it; however, when you don't know the kanji, learning a word for use in reading/writing is unnecessarily difficult because even if you remember how to say the word without kanji as a reference -- an increasingly daunting task once more words are thrown into the mix due to the small sound inventory -- you won't be able to read it (or write it without looking like a child) because it'll always be written in kanji anyway.
Where I live, basically nobody speaks Japanese, and I only rarely get an opportunity to interact verbally in Japanese. As a result, I've focused primarily on expanding my ability to read and write Japanese as a way to crack into the language, and because the grammar comes very naturally to me (...most of the time) I find myself spending the vast majority of my time spent studying the language on kanj because I simply cannot get a grasp on vocabulary without it. This method of learning vocabulary is as slow as molasses.
Heisig does away with this by offering a tangible way to remember what kanji look like without forcing you to also learn the readings and the usage at the same time. This allows you to identify words in written language without having to first understand and then become romantically involved with for a brief period each kanji in the compound. The traditional method of learning all of the elements of each kanji the first time you learn them is fine if you have no imperative to learn kanji to understand... anything, but when you do, it's just slow and inefficient. You aren't using the assigned meanings to learn words; you're using the assigned meanings to remember the kanji to learn words. The Heisig method simply extrapolates the technique that many learners do of assigning placeholder meanings to kanji they don't understand in words that they do to the entire language.
I'll use your example above (注意して下さい
. Specifically I'll look at 注意, because 下 is one of the first kanji learned and ください is also fairly common to see written in hiragana. It took me at least a few months of studying kanji to get to the kanji to read 注意; however, 注意 is probably one of the most common words in the entire language. In what other language is it reasonable to go through months of study to learn a word as common as 注意? Heisig eliminates that gap by giving you a tool to learn the word 注意 (and thousands of other words) without having to sit down and learn and compartmentalize 注 and 意. For one word, learning and understanding each kanji is not so bad, but Japanese has thousands of words and the vast majority of them involve at least one kanji character, so this becomes so cumbersome so quickly. A Heisig learner can make whatever imaginary association they come up with for 注 and 意 and would then instantly be able to understand that word, even if they don't exactly have a thorough understanding of the characters that make it up. The added benefit is that when your real (ie not RTK) kanji studying brings you to 注 and 意, you'll probably have seen them used at least a few times and will have less of an ass-backwards way of remembering how to read them.
Of course, it goes without saying that Heisig must be treated as complementary to actually
learning the kanji, as Heisig is merely a tool to help you parse sentences.