When should I replace hiragana with kanji?

Question

When should I write わたし instead of 私?

Answer 1

I cannot imagine any particular case that Japanese people have to write わたし instead of 私. To a beginner of the Japanese learning, I would like to advise to use 私 instead of わたし in any case.

As a Japanese writer, however, I often avoid using 私 in my writing, because I think it better to use hiragana when using the words originated in Japan, not in China. So my ideal is to write original Japanese words in hiragana and to use Chinese characters in writing many words originated in China. This is only my rule or ideal. In practice, however, I often have to use 私 instead of わた(く)し in order to avoid ambiguity due to a long sequence of hiragana.