"What does the man do?"

Translation: Mit csinál a férfi?

[germanboy_]

Mit tesz a férfi?

[anirudhbhide]

When to use Mi and when Mit?

[mizinamo]

mi is used when you are asking about the subject, mit when you are asking about the object.

Here, you're asking about the object -- "The man does ...." -- the "..." that you are asking about is the object of "does", the thing which gets done by the man.

[anirudhbhide]

Thank you very much!

[Elon_the_Hittite]

It's in the accusative case, if you want to be grammatical. "-t" seems to be a generic accusative ending for both singular and plural, which makes it somewhat easier than German and certainly easier than Latin.