There are two main ways to get to Machu Picchu. You can take a train from Cusco or Ollantaytambo to Aguas Calientes. Then you can take a 30 min bus ride up there or you can walk 8km.
Or you can take the Incan Trail. There is a 2 day and a 4 day trail and you must go with a touring agency. There is a 500 person limit for the Incan Trail. It looks like, the current cost for the 4 day hike (45 km) is around $400 and the entrance to Machu Picchu is about $90. There are other less popular trails that can get you to Machu Picchu as well.
I have wanted to go to Machu Picchu ever since I heard that it existed! It won't be one of the first things that I do because you have to be very careful with the altitude when you get to Cusco but I'm really looking forward to it! I want to hike the Incan Trail but I'm also nervous about that. I'm not much of a hiker so I don't know if I can really handle several days of hiking and then sleeping in tents. But I'm going to try and I'm trying to start hiking more often now to get used to it.