letters of recommendation

Im going to be a freshman next year and plan on rushing a fraternity. How important are letters of recommendation for getting a bid? Also who all can write a rec for me? Is it only alumni of that chapter or would alumni of the fratnerity at a different school be acceptable? What about current members at other schools or alumni of the school whose fraternity has folded? I know that an alumni of the chapter would be the best but if do not know someone who fits that, would it better to get one from one of the other above criteria or not submit one at all? Thanks