Make sure you have a good machine for hunting the beach. A land machine is OK for the dry sand, but stay away from the wet sand and the water with the land machines. I almost lost an E-trac to the waves as I was digging and a wave came out of no where and I was just lucky enough to snag the E-trac as it floated by. Luckily, there was no water in the control head or it would have been toast. From then on, it is strictly the Excalibur for me at the beach.
A good long handled sand scoop is a must. Get the largest you can handle. I personally use the Beach Brute in Florida. There are other really good scoops available. Going cheap on a scoop is not a good idea. I attach my scoop to my belt and drag it till I need it. That way it leaves a trail that shows me where I have been.
Make sure your valuables are not in the car. Hide your wallet and other valuables as thefts from cars is rampant especially in today's economy. Hide your cell phones, GPS or anything of value. Don't take your cell phone in the water! They don't work after getting dunked in the ocean.
A good hat and sunglasses are mandatory. Make sure if you are using a baseball cap that the little nubby thing on top is off. It will dig into your head from the pressure from your headphones. Don't put any sun screen on your face or anywhere near your head. You will get sweaty and the sun screen will find its way into your eyes. If you are wearing a hat and sunglasses, your face is pretty well protected and the headphones will protect your ears from sunburn.
Make sure you use headphones. The waves make a lot of noise along with all the people talking and asking you tons of questions.
Don't fear the sharks too much. Chances are that you will not have any problems with them but keep an eye out anyways. The sting rays need to be watched. To walk in the water, I do the stingray shuffle. I move my feet by scrubbing them against the bottom instead of a regular leg lift walk. That way if you get near a sting ray, you push it aside instead of stepping on it.
Watch and observe the people and where they put their beach towels. That is the towel line and many things are lost in the sand in those areas. Don't detect there till everyone has left though.
Walk ways to the beach are also a good area to detect as well as the area in the sand near stairs over the sand dunes. Don't dig the dunes though.
If you are water detecting, look for cuts in the areas near the water line. Also on the beach itself, look for erosion areas. They are the prime areas of the beach to hunt.
Don't show anyone what you have found. If anyone asks, tell them just a bunch of pull tabs. There are people that will take advantage of a situation and if they know you found a gold ring, you might have to fight. That's just the way the world is now a day.
Fill in all your holes on the dry beach. Pick up as much trash as you can. Beer is illegal on the beaches but you will find beer cans buried. Some beer cans I have found as deep as a couple of feet. Some are full.
If you are water hunting, then watch the waves. Sometimes you will get hit with a pretty good wave. I keep myself facing perpendicular to the beach so the thinnest part of my body gets hit and not my face or back. A good size wave will hit you pretty hard and knock you off your feet so making yourself a smaller target to the wave is a good idea.
If you are planning on water hunting, then a wet suit might be a good idea. The waters around Florida are still fairly cool and will start to warm up in mid March.