I don't do any stretches but I do elliptical and body weight exercises as a warm up. I have great flexibility, maybe it's genetic or maybe it's because the exercises I do require it and practice makes perfect.
I stretch only after I warm up, your muscles are like a rubber bands. If you put a band in the freezer, let it get cold, take it out and stretch it, it will break. But take that band out and warm it up, and it will be as loose as hookers snatch.
I do like to stretch during also, and post. Although I don't do that as much as I could.