You'll love Machu Picchu - it's somewhere I always wanted to visit, then when I finally made it, it felt seriously unreal. If I could give you just three tips, it would be the following:
1: Make sure you're there early or preferrably later, beating the crowds or hanging around after they've gone. the light is also better early or late, but get the hang of exposure compensation and shooting in RAW becuase it can be challenge to get the result you want.
2: For sure take the famous shots, but also explore the full site if you have time - you can easily get away from the crowds.
3: If you're staying in the Machu Picchu village at the bottom of the mountain, consider eating in the indoor market. Some great local food and considerably cheaper than the restaurants!
Here's one of my favourite shots taken at the end of the day - and for once I didn't mind someone - or something - walking in front of me as I took the photo!