As 和 like 可以混用的例子，意思都是“像……一样”。Like 比 as 稍微更非正式一些。
Nobody understands him as I do.
Nobody understands him like I do.
没有人像我一样理解他。
understand 动词，理解，明白

[as...as...]
I can't run as fast as you. 我跑得没你快。

used to 过去经常，曾经……
我跑得没有我以前那么快了。
I can't run as fast as I used to. 

Do as I do.
像我做的那样做。/ 照我做的做。

As 还有一些固定搭配：
as you know 像你（们）知道的那样，如你（们）所知
as you requested 按照您（你）的要求（request 动词，要求，请求）
as we agreed 就像我们说好的那样，正如我们所达成一致的（agree 动词，同意，达成一致）