Now I know it happens! But I wanted to know where are the best places to put some foam in your car to help stop the noise. I know in the trunk but does anyone have any specific places?
Don't use foam - user a sound damplifier like dynamat. The licence plate is the most common place for rattle. So start there. They sell a kit for 15 bucks that'll stop your plate from vibrating. Other common spots are the doors, roof, rear deck, floors, under the hood, and if you want to, throw some in the fenders. But that's maybe a little to far.
If you're just trying to stop rattles, closed cell foam will do the job. Doesn't even have to be closed cell if you are using it somewhere you know will never get wet.
License Plate.
Between the trim panel and sheet metal on the rear deck.
Between the trim panel and inner skin of the door.
Behind any trim panel and between any other objects that rattle.