orthography - Which writing system (hiragana, katakana, or kanji) should we use when writing out someone's name?

I know how to read hiragana and katakana, but know nothing else. A lot of people I know want me to write their names in Japanese. Is it right to write them in any system, or are there specific rules?

Answer

Names of Japanese people have a specific spelling that may be in hiragana, katakana, kanji, or any mix thereof. You should spell their name as it is spelled, e.g. 「田中けい子」 (TANAKA Keiko).

Names of foreigners are written in katakana, unless they have decided on the equivalent kanji they want to use. Or if they ask you to choose the kanji then do so paying attention not only to sound but also meaning when selecting them.