Example:
What does beer and wine have in common?
or
What do beer and wine have in common?
I've seen them both being used, the first form being more frequent, but I think the second form sounds more correct, although I can't be sure.
What do beer and wine have in common?
is the question form of
Beer and wine have __ in common.
The subject of the question is the conjunct 'beer and wine', so the auxiliary verb DO takes the form for 3d person plural: do.
The correct one is "What does beer and wine have in common?", because you use does with he / she / it and do with I / you / we / they. You can read more about it here