Honestly, there is not much to say here. The beauty of this place speaks for itself. But I do have some recommendations to get the most out of your experience here.
1. Make sure the group you are going with is actually going to spend some real time here. Many travel groups only spend a few hours here. You will want more time here. You have just to wander around and imagine what life was like hundreds of years ago. We arrived there midday and stayed for the whole next day and then half the day after that. It was just the right amount of time.
2. Bring good hiking boots. There is a lot of walking and some great optional hikes if you have the time.
3. Bring a good camera and lots of film. Theft is always a problem when traveling, but you will regret not having the best camera you own here. Bring it and protect it. It will be worth your effort.
4. Get there earlier and stay late. You will get to see the ruins with the least number of people if you are there earlier in the morning or late in the afternoon. This will give you the most alone time in the ruins, which is a great experience. Plus, being able to see the sunrise on Machu Picchu is a once-in-a-lifetime thing.
5. The food at the gate is very expensive. Bring your own water and Clif bars so you won’t have to buy as much up there. Save your money for a good alpaca steak in Aguas Caliente.
Finally, say hi to all the llamas for me. The Peruvian government keeps them there to cut the grass, but they look like fun pets.