When to use Hiragana, when Katakana?

[TokyoT]

I dont know for example, whether I should use 窶堙 or ﾆ男 . Both are meaning "Ni", so "two"
When exactly i use Hiragana, when Katakana?

 

[Zlarp]

When do you use quotation marks or italics or bold text or underlined text or exclamation marks?

Answer: Whenever you feel like it and it's not wrong.

How do you find out if it's wrong? Read a lot.

 

[Mike Cash]

"Ni" doesn't always mean "two".

 

[Toritoribe]

I dont know for example, whether I should use に or ニ . Both are meaning "Ni", so "two"
When exactly i use Hiragana, when Katakana?

In the first place,what you wrote/typed/pasted is a kanji 二, not a katakana ニ.

See the wiki page linked below.
Japanese writing system - Wikipedia, the free encyclopedia

 

[BrianLewis]

For a beginner, katakana is used for foreign words: アメリカじん for example. Later on, it's used to emphasize a word.

 

[Zlarp]

I've also found furigana for foreign words written in kanji that uses katakana. So "船長" had "キャプテン" as its furigana instead of "せんちょう", which I find is rather clever.

 

[BrianLewis]

That's a good point. You know what the person is saying, yet also know the meaning.

 

[dwcarless]

I've noticed that personal pronouns (especially in song lyrics) are sometimes written in Katakana. Is that for emphasis, or is it just stylistic?