[Article] All about Japanese Grammar (well, not quite)

Basic Word Order
I believe that one of the key fundamental aspects of understanding a foreign language is also understanding the grammar used to assemble (or disassemble) sentences. To start with, Japanese basic word order is...

Subject -- Object -- Verb

For example, the English sentence,
"I play KiCL." -
would be rearranged as...
"I KiCL play."
where "I" is the subject (who is doing it?), "KiCL" is the object (what is being "done"?) and "play" is the verb.
(Note that in Japanese pronouns are often omitted if they are understood by context, so in this case if the subject I is already understood, then it's perfectly fine to say, "KiCL play.")

Particles
Another important part of Japanese grammar is particles. Particles are used to indicate a words function in a sentence. Japanese also does not have equivalent words for "a, an" or "the" (called "articles").
Basic examples of particles are as follows:
(note that this list is not complete and does not list every possible use for each particle)

は - Pronounced "wa" but written "ha", it is used to indicate the subject of the sentence (special note about this under が) Example:
あなたは　日本人　です　(anata ha nihonjin desu)。　
You are Japanese.
This particle can sometimes be thought of as "as for".
("[As for] you, you are Japanese.")

も - Means "also" or "too", as in "me too".
あなたも日本人です (anata mo nihonjin desu)。　
You (also) are Japanese.
この漢字も難しいです (kono kanji mo muzukashii desu)。　

の - Possession or sense of belonging. Sometimes "of", "belonging to" or "about". Can make nouns into adjectives. Some uses for this particle are:
わたしのほん　(watashi no hon)
"My book"
あかいのほん　(akai no hon)
"Red book"
*Note these sentences can also mean "My books" or "red books".

を - Pronounced with barely any "w" sound, it is often romanized as "o". Marks the direct object of a sentence - the object that receives the action of the verb. For example,
ほん　を　かいました　(Hon wo kaimashita)
"I bought (the, a, some) book(s)." The book is the thing being bought.

が - The particle ga can be used to introduce a subject for the first time in the dialogue the same way ha/wa (above) is used and is also used to mark the object in a sentence.
わたしは　ほんが　すき。
I like books.

に - Ni has several uses...

* Time or date of action
(今日にかいました　{kyou ni kaimashita} "I bought it today")
* Person at receiving end of an action in sentences with the verb give
わたしは　あなたに　ほん　あげます。 (Watashi ha anatani hon agemasu)
"I give you a book."
* Giver of an item with verbs meaning "receive"
わたしは　あなたに　ほん　を　もらいます。　(Watashi ha anata ni hon wo moraimasu)
"I received a book from you.)

へ - He indicates direction (west, right, forward) or destination (Japan, Europe, my house) of travel.
日本へべんきょうにきました　
I came to Japan to study.

と - Indicates person with whom an action is completed and joins nouns in a complete/finite list. だれと?　dare to? "With who?"　
私は本と漫画と雑誌がすきです。　(watasi ha hon to manga to zasshi ga suki desu.
"As for me, books and manga and magazines are likable" ->
"I like books, manga and magazines."　
*Note that "ga" is not required in this sentence.

や - "Ya" acts like "to" except the list is not complete - like a list where you might add "etc..."
私は本や漫画や雑誌がすきです。 (Watashi ha hon ya manga ya zasshi ga suki desu.)
"As for me, books and manga and magazines, etc... are likable." -> "I like books, manga and maganizes, etc..."
*Note that "ga" is not required in this sentence.　

から - When placed at the end of the first clause it makes the sentence have the idea of "because".
私は上手じゃありませんから　あたらしいです。Watashi ha jyouzu jya arimasen kara atarashii desu.)　
"I skilled am not (because) new am" ->
"I'm not skilled because I am new."

なら - When places at the end of the first clause it makes the sentence has the idea of "if".　あなたはアメリカ人ですならアメリカにいますanata ha amerikajin desu nara amerika ni imasu "If you are an American you are in America" (this sentence not always true :p) It is also correct to say やすいならかいます yasui nara kaimasu "Cheap (if) buy" -> "If it's cheap, buy it." because the pronouns can be understood from context, and you don't use adjectives in this case (the adjective being やすい)

ね - A colloquialism, sort of like "You know?" or "Isn't it?" used liberally at the end of a sentence (practically any sentence ranging from ですね?　It is, isn't it? / It is, you know? to　あなたは上手ですね　You're skilled (at this) aren't you?)

よ - Adds emphases to a sentence, similar to an exclamation point. 大きいの本ですよ!　ookii no hon desu yo! "It's a big book!" (I guess in this case you might say "It's a huge book!")

Phew. I'm not done, and will edit this post with more information (and corrections/etc as listed above) later. Hope you enjoyed this! ^_^ Please practice your Japanese - look for new verbs and new nouns to practice with, write what sentences you know how to write and play with what you have. IMO, the best way to learn is by doing, and if you don't use it, you'll lose it!

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Thanks to Willuknight for help with formatting

(by Aikeru)