Well, I start in the parking lot. As I am walking from the car, down to the beach, I detect the paths where people are similarly parking and heading down. This is where they loose keys, coins and other things in their pockets. They usually loose stuff on the way back from the beach as they are getting the keys out of their pockets or bags... However, this is one prime area where you will find things. When I am done detecting, I do the same. I detect a path from wherever I am back to the car. Use the well worked trails and such.
While down on the beach look at the facilities and layout. Vending machines, restrooms, drinking fountains and concession stands are all places where people might loose money while making change or going through their pockets for a comb or any other items. See if you can spot areas where people play frisbee or volleyball etc. Those areas would be good also. Sometimes there might be an actual volleyball pit where there is a net. Search around the pit as well as along the sidelines. People pile their belongings along the sidelines while they are playing. Things fall out of pockets and bags and into the sand. Perhaps up along the net, re volleyball, would be good. This might be where someone might go after a ball in a way where a ring or bracelet might fly off.
Tot Lots are also good. Some of our beaches have elaborate play sets for young children. Check under any place where children might hang inverted (upside down) or where they might be climbing around. If there are park benches anywhere on the beach, check there. Mothers will sit and watch their young children while they dig in the sand or burry toys. Also, people might loose money from pockets when they sit on a bench to tie a shoe or take off a jacket.
I was on a local beach one day and there was a large branch fallen in the sand. It was more of a large tree limb. I searched in front of it when I got there but access around it was a little limited. While I was down there some kids came along. One boy, about high school age, was showing off to the girls and lifted the branch and moved it about 2 or 3'. After they all left, I went back over and checked the area behind that was previously not accessable. Under where the branch was, I found about 6 quarters in a 2'x2' area. I can only summize that someone might have hung a jacket or some warmup pants there and their laundry money fell out or something. So, if you see a fence or a fallen tree or again, the park benches and play equipment search around these areas as people might hang articles of clothing on them while down on the beach.
Every time I go down to the beach, I do plot off an area of the sand where people might lie around sunbathing. It is an aweful large area so I can't do it all in one shot. Depending on the time I have, and since I am more in this for the activity not what I find or getting rich at it.... I just cris-cross around an area til I find something. I do it somewhat methodically but in a sketchy kind of way. Once I do find something, I recognize that things often get lost in quantities. So, there might be other things near by. I figure that a lost coin or key or something is an indication that this was where someone was laying in the sand. I then start a circle of sorts, radiating out from what I found, covering about the area of someone in the sand. Usually, a dime will lead to a couple pennies, a quarter and a nickel or two. I haven't had much luck with jewelry really. Lots of times, when I find someones lost quarter, I then find their candy wrappers and beer caps also. Incidentally, when I search and I do find a beer cap, or even the foil cover from a juice bottle, a juice box or other trash, I still plot and search the area. People sit around in groups. One beer cap often leads to 2 or 3 or 4. That might tell you, especially if they are of a couple different brands and all similar in age, that a party was held there. Beer caps cold lead to an earing or a watch. Juice boxes tell you that a child was there and so, probably was a parent. So, this could have been a spot from a beach blanket and other things might be near by. Anyway, when you find something, search that immediate area thoroughly. Then, when I figure it is clean, I move on to another area till I find something else.
If you have the time and are spending the whole day on the beach, do plot off a managable area and search it more completely and systematically. Go back and forth in straight lines and such.
I haven't done much along the water line but that is supposed to be good also. People wading in the water will loose ankle bracelets and toe rings. When they reach in for shells or rocks they might loose a ring or bracelet. In areas with tides, as the tide goes out, it takes things from the beach and starts to draw them out. So, you might find some of that in the water. Also, areas with tides have the added possibility of Sand Bars. Where the sand being pulled out is deposited and the floor of the ocean rises there is a trough where a lot of stuff washed off of people and left on the beach can come to rest. At Low Tide, when this area, and the area of the sand bar, are exposed, take avantage and search these areas. People often go way out at low tide and and loose things while wading on the sand bars. These areas might not get searched a lot as they are not always accessable. Some times, they could be under 6 or 8' of water. When they are exposed or under only a foot or so, they are easier to search. Again, the area beach side of the sand bar could be, sort of, a trap for stuff washed off the beach. Items get plled down the slope until they come to rest in the low spot right in front of the sand bar.
Then, any time there are heavy storms out over the water, even if your weather on shore has been nice, go out and search around the water line. As the waves come rolling and roaring in, they turn up stuff that was burried under settled sand. A lot of that stuff on and around the sand bar, can be kicked back on shore by the turbulance of the rolling water.
In any case, as you mention, beaches can be quite large areas to cover. So, like I have been suggesting, I look at the layout of the area and spot the high possibility areas and search all those. Then I move on to the wider areas and cover them with as much time and effort that I can afford.
