Okay so the first person will choose truth or dare. The second person gives them either a question for truth or gives them a dare to do. Then they choose one. I hope that helps.
Example:
Person 1: I choose truth.
Person 2: What is your favourite TV show?
I choose dare.
Person 3: Go and post 10 pics of Sanaya Irani in Channchann forum.
I choose truth.
Person 1: @Person 2: Adaalat
@ Person 3: Why do you like Twitter?
I choose truth.
and so on...