[Archaea]

Originally Posted by nikuman

Well, you've opened a can of worms there....

With the disclaimer that I'm quite rusty on the book-learnin' behind this, there's about 10 or so uses of wa/ga that are discrete. Ga is used as an object marker instead of wo with certain verbs/descriptive verbs (notably dekiru) (zo wa hana ga nagai, lit. "as for the elephant, [his] nose is long" or, as I would translate it, "elephants have long noses"). Ga is also used when indicating that the stated subject is exclusively doing X (boku ga iku, indicating that only I will go). Ga is also used as a marker for the affected party in a passive/affective setting (boku ga haha ni shinareta). In addition, ga should replace wa in all subordinate clauses.

Wa, on the other hand, can usually be consider a particle that designates an "as for X" sort of idea (see the elephant sentence above). It is also used to emphasize the noun which it follows in order to contrast it to other nouns not used (i.e., boku wa iku can be translated as "I will go [but I make no claim as to you]". Which makes sense in the "as for X" explaination.

There are a few more rules that I've forgotten but still (presumably) use in speech. I'll have to consult my old college notes to remember them all.

As I am self-taught, any helpers I can get I appreciate.