Japanese writing: how do you know what characters to use?

Katakana is generally for imported and technical words. Hiragana is for native words. Both character sets a have the same sounds.
Back in the old days women and kids used hiragana and men used Kanji.
Often you will see small hiragana written next to kanji as helpers so you can pronounce the word.

Hiragana and Katakana represent the same syllabary, but they are used for different purposes. Generally speaking, hiragana is used for Japanese native words, and katakana is used for words not of Japanese origin. In regard to writing words you have only heard pronounced, you have to memorize which characters are used for that word in order to spell it properly. A tip is that most adjectives and verbs are spelled in hiragana since the Japanese have their own words for these, and all particles use hiragana characters. Typically it is nouns that originated from a language other than Japanese that are spelled in katakana. An example of katakana use would be the word “basurumu”, which is the Japanese word for bathroom. This word is spelled with katakana as バスルーム. The word coffee, which is “kohi” in romaji, also uses katakana, and is spelled as コーヒー. It is important to note though, that most words in Japanese have a kanji character that is used instead of solely using hiragana. For example, the word tsunami, which in hiragana would be つなみ, is actually written as 津波 by using kanji. In order to be literate in Japanese you will need to learn all three scripts and their proper usage. Also, you should know that hiragana and kanji are often used together, even in the same word. It is difficult at first but just keep studying and it will make sense to you eventually. There are plenty of resources on the internet for this.

Any more questions? I will do my best to make this clear since I realize internet lessons can be confusing at times.

Keep in mind I do not speak Japanese as a native language and my fluency is minimal. However I have been studying it for some time.

Edit: My co-worker is studying Japanese and saw this as I was surfing Fluther and wanted to answer it lol.

Thanks for your help, both of you.

Any idea why there are two syllabaries at all? Why don’t they write loanwords in hiragana too? Who invented katakana, and what for? Was it deliberately created to make a difference between men and people who are not men?

@Blackberry
“Also, you should know that hiragana and kanji are often used together, even in the same word.”
So I see… Just yesterday I came across 見る miru, the verb “to look”, the first syllable in kanji and the second in hiragana. Is that because the “ru” part is the verb inflection that has to be able to change with usage?
I’m not sure if Japanese verbs even inflect at all, except maybe for tense.

What does ー stand for? Is it elongation of the previous syllable?

You have the big picture. Think of the kanji part as a concept or idea and the hiragana part like a modifier. The words are still Japanese so they must be in hiragana.
By using katakana it give you a heads up on the meaning. If it is katakana your great-grandparents didn’t know about it.
Another little quirk I have found conversationally is the lead in “Ah no…” It is like the baud rate.
Technical guys love katakana. (Imported, new words) All the exotic chemical names are in katakana. The old, boring stuff like gold silver, sulfur are in kanji.
Occasionally, you will find a young 20’s female writing her name in katakana instead of the kanji her parents gave her, to show here independence and free thinking. Kind of like Stefani Germanotta calling herself “Lady Ga Ga” except the name doesn’t sound like something an infant would babble. Sensible, conservative guys avoid them.

I see… Thanks.
Do you know what ー stands for, too?

Yes. It is like an extended vowel コーヒー is koo hii, コヒ is shorter: kohi.

That’s what I thought.