I know this may sound weird, but try it. The easiest way is to sit on your bed or another soft surface and just slowly lean back. It's a weird sensation that I can't describe in words! It's oddly relaxing though.
Another way to do it is with your hand, but I feel that the best way is by leaning back.
Another way to do it is with your hand, but I feel that the best way is by leaning back.