Find out if the campground you plan to visit requires reservations in advance. Then, start a list of things you might possibly need. Keep in mind that you can't count on the comforts of your home, no electricity means no video games. Also, include a first aid kit.
Rain, in some areas, can be unpredictable. Have a plan in case the weather deteriorates. Be prepared to endure the sun for long periods of time, there is not a lot of shade. There is no lifeguard on duty and this area of the beach has warning signs for frequent, strong currents.
I like to go to the beach either early in the morning or late in the evening. While a sunny day is great, the sun can be merciless in the Outer Banks.
We have been visiting Cape Hatteras for the past four years and I have found that going around mid-July is the best chance to have almost perfect weather.
Camping is pretty cheap overall. You just need to have a tent and be able to provide your own food. Eating sandwiches for breakfast and having hot dogs and hamburgers for lunch or dinner will do and will save you money. Bring plenty of snacks and water as well.