1 You'd better not wear a T-shirt today.
had better 是最好的意思
这两个词组合在一起当做情态动词,也就是后面直接加动词原形,否定式在better后加not,再加动词原形.
例子：You had better go out for a walk.（你最好出去走走）
You had better not go out .你最好不要出去.
注意,You had better 可以写为 You'd better
2 The documentary will show the tourists what Beijing is like today.(改how为what)
like作介词,而作动词：
How do you like…?句型主要用以询问对方对某个地方或某件事物等的看法,意为“你觉得…怎么样?”
How do you like the city?你觉得这座城市怎么样?