Main verb
I can only do what I can do.
That should do the trick.
Would you do the honours?

Auxiliary verb (helping verb)
Do you find it hard to meet all the deadlines too?
I don't feel comfortable talking about that.

Substitute the main verb
You hate mushrooms. So do I.
Do you take the No. 58 bus? So do I.

Imperative verb
Do your homework
Do your revision (for exams)
Do the dishes
Do the garden
Do the car
Do the clothes
Do the laundry

Added stress (do + main verb)
Do let me know if you need me.
Do call me tomorrow.
Do take care.

'Do' as the noun
We're going to a family do at the weekend.
They're planning a work do for Christmas.

I like your hairdo.
Is that a new hairdo?