Aww, a beach day. Whether you've planned the day weeks in advanced, or it's an impromptu to jaunt to the shore, you must be prepared to set up camp when you arrive. Be sure to pack the essentials, and be aware of the time you are planning to arrive at the beach. This will determine how crowded it is. The earlier you get to the beach, the more options you have in choosing your spot for the day. If you and a friend are hitting the beach with only beach chairs, you can arrive at any time and get a decent spot. However, if you, the family, friends, cousins, etc. are planning a massive beach day, it's really best (for you and other beach goers) to arrive early, by 10:30 AM, to set up (earlier if it is a holiday weekend). Please, think of others. Everyone wants an enjoyable day, so don't bring items that will take away from others experience or kill the atmosphere.
When you arrive at the beach, unpack the car closest to the beach entrance and carry your belongings to the sand. Keep in mind when you're packing that you will have to carry your stuff to and from the beach! There is no bellhop. Put down your towels, chairs, cooler (or if your on the East Coast, your beach blanket, preferably an old, Pendleton one, and not a ratty fitted sheet or something). Place your heavy items on the corners of the towel/blanket if it is a windy day.
Please remember that the beach is not Oklahoma Territory in the 1870's; if the beach is crowded, you may not attempt to spread your stuff out over as much space as possible. Conversely, if the beach is not crowded, you should leave a good distance between your blanket and that of your nearest neighbors. Then, enjoy your day!