where is the drain pipe plug on the radiator on a 2006 chevy trailblazer
the petcock is usually located on the lower side of the radiator. Check the outer sides on the inside of the radiator. The side facing the engine. Sometimes you can reach it from above, if not the you have to go in from below. You might have to remove a trim panel or two to access.
which side is it on driver's side or passenger side
It doesn't have one. You have to take the bottom hose off to drain the coolant.