Luggage and bags:
Clothing/Shoes/Weather Gear: Make sure you bring a sheet to sit o the sand with, some sun tan lotion cause our sun actually gets real hot up here and definately some sun glasses. This is of course if it is the summer otherwise wrap a mattress around you because it is colder here then in the city due to winds off the ocean.
Toiletries and Medical Supplies: Bring yoself some bug spray with DEET in it. Our ticks and mosquitos know how to give out diseases so watch yoself. After being in wooded areas make sure you check yourself for ticks, closely that is cause a Deer Tick is the size of a grain of sand.
Camping/Beach/Outdoor Gear: A tent would be a major plus because there are many places you can set up in the county parks, state parks, and National sea shores. Some of my favorite memories of LI is sleeping in a tent and waking up at the beach.
Photo Equipment: I never leave home without it. If the luggage is heavy this would be the last thing to subtract, underwear are less important by far.
Luggage and bags: This will help if you are one to run from the sun. I take it all in, this one was my brothers. Look at those colors!