When used as a preposition "like" is always followed by a noun or pronoun. It means similar to or the same as:
I look like my mother.
They have so many animals. Their house looks like a zoo.
What star sign are you? I'm Gemini, like you.
You're stupid. Why do you say things like that?
I work like a slave = very hard. (I'm not a slave)
- We use "as" in comparatives and with the same as:
You are as tall as me.
She works in the same office as me.
Barbara’s suggestion was almost exactly the same as mine.
- "As" is used to indicate people's professions or the role or function of sb or sth:
He works as a waiter.
He works as a slave = he's a slave.
An electric drill can also be used as a screwdriver.
- When "as" is used as a conjunction, it is followed by a subject and a verb:
Do as I say and sit down.
Don't eat and speak at the same time, as my mother used to say.
As you know, we're leaving tomorrow.
- As is used after certain verbs, for example, define, know, refer, describe...
Officers described Jorge as a "greyhound".
- "As" is used in the expressions as usual and as normal:
Jorge continued his life as normal.
EXERCISE WITH VERBS FOLLOWED BY AS
You can read the theory here and here
You can do exercises here and here