～こと

こと turns a verb phrase into a noun, so it can take は, が or を and sit where a noun would: "playing the piano", "to go to Japan". It follows the plain form of the verb, and the tense of that verb stays as it is.

The phrase before こと is a full clause and can carry its own subject, marked with が or の: かれ彼がくる来ること, "his coming".

こと or の

の also turns a verb into a noun, and with words like すき好き, たのしい楽しい or むずかしい難しい either one works; の is more casual. Each has places where the other is wrong.

Before です and in fixed patterns such as ことができる, ことがある and ことにする, only こと works.

• × 夢は日本に行くのです → 夢は日本に行くことです

With verbs of seeing and hearing, and with まつ待つ and てつだう手伝う, only の works, because you perceive or help with the action as it happens.

• × 彼が歌うことを聞いた → 彼が歌うのを聞いた

こと at the end of a rule

A notice or a list of instructions can end on a dictionary form or ない-form plus こと. It means "must" or "must not", and it belongs to writing.