I do the same as Megahurts but I do it with black & white sheeting. Just open the door as far as it will go, measure the distance between the inside side wall and the door, cut the poly sheet to fit and fix into place with your chosen adhesive.
The sheeting folds up naturally (cut the right way on the roll of sheeting

) and blocks all light and most of the air.
Draught excluder tape is a waste of time. It
WILL peel off - not neatly either! Don't waste your money on it lads and lasses for the adhesive will fail.
Edit - draught excluder tape is perfect for the top and bottom of the doors, but not the hinged side.