I've searched and searched but can't find the thread someone posted about the 8 or 10 things you can do to a song to make it more dynamic, such as changing octaves, tempos, etc. It should be a sticky. I'm trying to take some of my band's tunes and make them....well, better.
i think that the best way to make a song more dynamic, and definitely the easiest, is to at one point slow down and let up a bit, and let the song sort of catch up to itself, and when you get the crowd's attention by changing it up, go back to the higher energy you were at before, my band does this with curtis mayfield's "Move on up" and we at one point have just horns playing with snare on one and three, and when we go back to the groove the crowd goes nuts.