Take good walking shoes and wear 'cool' clothes so you don't get too hot out there in the sun...even early in the morning it's still VERY hot.
Photo Equipment: Take lots of film or memory cards, you'll need it!!
Miscellaneous: Take some sunscreen, sunglasses, a hat and lots of water... It gets VERY hot and you'll wish you had a portable air conditioner... ;)
Luggage and bags:
Take a camelbak or some form of hydration pack. The water will stay cold in the camelbak for about an hour.
Clothing/Shoes/Weather Gear: Open style sandles are best for walking around the monuments. Expect to change your clothes after being out in the sun for an hour. They will be soaking with sweat.
Toiletries and Medical Supplies: Antisan and Malaria tablets
Photo Equipment: Take the biggest card you can afford for your camera or take lots of small ones and store them when they are full. Be careful camera's get very hot, when out in the sun.
Don't let the locals take pictures off you. Once they have your camera, they won't give it back without you parting with a lot of money
There is about a 5 minute walk from the bus/car drop off point to the temples, and the ground around the temples is quite uneven, so I would recommend sturdy, sensible shoes.
If you are sensitive to the sun, a hat would be a good idea, and sun glasses are a must - it is pretty glary here, with the sun reflecting off sand and water.
Photo Equipment: I think it goes without saying that a camera, with plenty of film/cf cards/batteries is a must!! Won't tell you how many photos I took....thank goodness for digital cameras!!
Miscellaneous: Bring some water with you down to the temples. Once you do the 5 minute walk from the parking area/shops, you won't want to walk back mid-visit to buy drinks.