The following paragraphs are from The Elements of Style by Strunk and White, the popular reference on proper writing in English. I don’t always agree with The Elements of Style, but this gave me a bit of a chuckle.

Like. Not to be confused for the conjunction as. Like governs nouns and pronouns; before phrases and clauses the equivalent word is as.

We spent the evening like in the old days. Chloë smells good, like a baby should.
We spent the evening as in the old days. Chloë smells good, as a baby should.

The use of like for as has its defenders; they argue that any usage that achieves currency becomes valid automatically. This, they say, is the way the language is formed. It is and it isn’t. An expression sometimes merely enjoys a vogue, much as an article of apparel does. Like has long been widely misused by the illiterate; lately it has been taken up by the knowing and well-informed, who find it catchy, or liberating, and who use it as though they were slumming. If every word or device that achieved currency were immediately authenticated, simply on the ground of popularity, the language would be as chaotic as a ball game with no foul lines. For the student, perhaps the most useful thing to know about like is that most carefully edited publications regard its use before phrases and clauses as simple error.