Comment by devilbunny

In this case. It's hard to make a firm rule because you can construct sentences with both words in them that aren't wrong-sounding, because the same word can be used in subtly grammatically different ways.

A good rule of thumb is to phrase the sentence as a question and see if it sounds correct. "What does it look like?" is fine. "How does it look?" is fine. "How does it look like?" does not. In the question "Like how?", "like" is more akin to "I said, like, what do you want me to do?" - I'm no linguist, but they do have a term for that use.