Treats, tennis ball reward (yipee!), I used the clicker a few times over a year ago and he really seemed to respond, but, since I'm not training "professionally", I kind of let it slide. I found an old one yesterday, clicked it, and guess who came running, ears at full alert! About the only time I've actually used NO was what I call the power NO. Dog is off leash, threatening to get into serious trouble--Loud, low pitched, "I mean it this time" NO! Then when the dog jumps ands looks (he's never heard that tone before) I call him in with those happy, high pitched baby joy sounds (think Richard Simmons) something like "Come SEEE me, come SEEEE, look, look, come SEEE!" Comes running every time.
Another thing I do, which I've never really "trained" the dog to pay attention to, is a relatively loud, high pitched sort of yip-bark (said once) that projects over a distance. I use it for the message "you're too far away; come back and join the pack." They really respond well without any training, not necessarily coming to a formal COME position, but coming back in close by. I kind of wonder if the sound might sound like some sort of communication bark a pack leader might use to a straying member.