最好【zuìhǎo】

最好 before a verb phrase means "it's best to" or "you'd better". It gives advice or a mild warning, and it stands after the subject or, for a little more stress, before it.

The negative is 最好别 or 最好不要: "you'd better not".

最好 as "the best"

Before 的 and a noun, 最好 is the superlative of 好: 最好的朋友 "best friend". The advice 最好 is always followed by a verb phrase.

Not for the past

最好 gives advice about what hasn't happened. For "you should have" about the past, use 应该.

• × 你昨天最好来 → 你昨天应该来

还是 is the other "had better": it says the speaker weighed options and chose, where 最好 just advises.