I would like to be more flexible because I practice Brazilian Jiu Jitsu. My question is how do I become more flexible? My friend and I had a small argument on the subject. He told me that in order to become more flexible you must perform dynamic stretches where you would "bounce" on the stretches and I told him static training is more important where there is no action and you would just hold that stretch for a period between 15-20 seconds. Which is correct so that I can work on which ever stretch?

I have a few flexibility books and they spoke about dynamic stretching and static stretching and from what I understood static stretching was the way to go in order to advancing flexibility.