最 (zuì) means "the most". Put it in front of an adjective or a verb like 喜欢 and you get the English "-est" or "most": 最高 is "the tallest", 最喜欢 is "like best". It is a key word of HSK 2.
Subject + 最 + adjective.
最 always comes directly before the adjective. You don't need 是, and you can't add 很 or 非常: 他最高 is right, 他最很高 is wrong. The group you are comparing within usually comes first, for example 我们家 (in our family) or 三个人里 (of the three people).
最 also goes before verbs of liking and wanting, such as 喜欢, 想 and 爱. 我最喜欢 means "I like best" or "my favourite is".
The most common mistake is to follow English word order and put 最 after the verb: 我喜欢最茶. 最 must come before the verb: 我最喜欢茶.
To say "the best friend" or "the biggest room", use 最 + adjective + 的 + noun. The 的 is needed: say 最好的朋友, not 最好朋友. 最 can never go straight before a noun.
If you want to use 是, end the sentence with 的: 他是最高的. 他是最高 on its own sounds unfinished; 他最高 is simpler.
To ask which one is the most, use 谁 (who) or 哪个 (which one) before 最. The answer keeps the same word order: 你们班谁最高？ 我们班王明最高。
最不 + verb or adjective means "the least": 我最不喜欢 is "what I like least".
Three common words start with 最. 最近 means "recently" or "lately", 最后 means "in the end" or "last", and 最好 before a verb means "you'd better". Like other time words, 最近 and 最后 go at the start of the sentence or right after the subject.
Practise this grammar point on paper: 20 exercises using only HSK 2 words, with an answer key on a separate page. Free to print and copy for your class.
Every example on this page uses only words up to HSK 2. Paste your own sentences into the level checker to see which words, if any, are above your level.