Like and as -- one a preposition, the other a conjunction

from Ruge Rules

The Rule: Like is a preposition; as is a conjunction.

If the comparison is between two persons or things, use like.
If the comparison is between two ways of doing something or between two states or conditions, us as, as if, or just as.

Examples:
Like me, he plays the piano. (We both play the piano.)

He plays the piano just as I do. (He plays the piano in the same manner that I do.)