1997 buick park avenue electrial problem

if a car off battery overnight that means their is a problem somewhere in the car.it sure that some thing is having positive down and area to check are radio component,check if the fans dont have extra relay,check if fuse is not put in a vacant space or relay and also check if the car do not security or if the centre lock is not working down or if wrong connection of wires are not done and also check the roof light.etc