When you open up the car and finally find what is loose what do you use to stop the rattle?

Some say foam(where do you buy it at and what brand,what is the real name of it)

Some say velcro, how do you aplly it in a way to stop the rattle. Just a quick emplanation would be greatly appreciated.

 

I know this may sound a little acward but I used a limbsaver, they are used on compact bow arrows to stop vibrations and sounds due to vibrations i put one bhind my right pillar cut of course, and one on my back passenger side pillar near rear window and now there are no rattles...I guess I just kinda "jerry-Rigged" it but it works...just a suggestion.