Look at the beach and see where the people are, all beaches have zones where people go. I prefer to hunt waist deep to about 20 feet from waterline in wet sand at first, look for low areas, look for areas where there are heavier objects laying on surface, (shells rocks etc), look for tidal pools close to water line.... If and when you find a good target do a spiral search out from the good target for about 20 feet, like weight targets usually get deposited together unless it is a recent drop.... I once found 3 rings this way whre if I had dug the one and moved on down the beach I most likely would have missed the other 2.....
Loke Lorraine said, the low tide line where the water hits the shore is a great place to look, have found many there myself as well.... Remember people are in the water at high tide too, so look where the high tide line is and work back to wards the water from it......
One of the best things you can do is take the time to observe the beach, see where people congregate.....