had best used to suggest an action or to show that it is necessary 用于建议采取行动或表明有必要；最好 You had best tell her (= it would be wise if you told her) that you won't be able to come to her party. 你最好告诉她你不能参加她的聚会。 We'd best be going now (= we should go now). 我们最好现在就走。