From Cuzco you can take a mini bus to Chincheros to visit the ruins, Maray (incan agriculture) and las Salinas. Form there you can hike until you reach the highway and take another mini bus or hitchhike until Ollantaytambo. There you are going to find more inca ruins. It is impressive! Do not miss out to stay one night in this beautiful village.
To reach Machu Picchu from Ollantaytambo, you can take another mini bus. Ask the driver to drop you off at Kilometer 82 of the train that leaves the station in Ollantaytambo. From this point you can walk along the rail until Aguas Calientes. It is worth walking it, although it is going to take you about 7 hours. Along the impressive scenery you will enjoy the beauty of nature. Here the rivers run in their ancient beds, free and overwhelming in their energy and sound. If you are able to spend some extra time and effort you should not miss those views. This walk is very different to the one most visitors would do. They would go directly by train and miss a big part of this energy and beauty. To walk up to Wayna Picchu, you need to purchase a ticket in advance in Cuzco or online. This link is helpful: http://www.machupicchu.gob.pe/. Each day only 400 Persons can reach up the famous mountain in the back of Machu Picchu. You should try to take a tour to the entire complex at 6am. I hired a guide for 2 hours in Machu Picchu and it was magnificent. Around 8am you can then walk up to Wayna Picchu. Going up there is definitively worth the pain. There are ropes to hold you and the ascension is very steep, but you are going to be safe. From Aguas Calientes back to Cuzco you can walk until Hidroelélectrica where you will reach the first piece of highway that leads to Cuzco. This walk is also along the train rails through the jungle and is very nice too. And back to Cuzco!