I think I’ve posted this before, but the very best tip I ever got from watching Tipical Mary Ellen was this:

Save the tube from inside a roll of wrapping paper. Cut a slit in each end. As you take lights off a tree, slip one end of the string in the top slit, then wrap the lights around the tube. Slip the plug in the bottom slit. They’ll be tready to unroll without tangles the next year.