do,did,does

If you are talking about 'do' for questions:

DO / DOES is for Simple Present:

I, you, we, they DO
He she it DOES

Do I have mail?
Do you want a cookie?

Does he like coffee?
Does she speak German?
Does it work properly?

Do we have to pay?
Do they eat meat?

DID is Simple Past for ALL persons:

Did I hear that correctly?
Did you pay the bill?
Did she buy a new car?
Did we go there?
Did they have a good time?
Source(s):
Teacher of EFL