Decide on which trek you want to take. The trail from Cusco to Machu Picchu is by far the most popular (and considered the "original" trail), but there are others, including the trail to the famous archaeological complex of Choquequirao. There are also alternative trails to Machu Picchu. The treks range from easy to difficult, so be sure you consider a trek that is right for your physical abilities.
Decide how many days you want to spend trekking the trail. The standard trek is four days and three nights. But some tour operators have two-, five- and seven-day options as well.
Choose where you want to register for the trek. You can buy the trek either in your own country or in Peru. If you register in your own country, you'll have the advantage of being able to reserve with a well-known company, pay with a credit card, and have someone to take care of hotel reservations and travel insurance. If you register for the trek in Peru, you'll likely pay about 50 percent less, but you'll only be paying the fee for the guided hike and incidentals.
Select a tour operator. Search the Internet, or flip through guide books for tour operators who can meet your requirements. Make sure to ask the company whether they operate the trek themselves or whether they're basically travel agents. Better to go with a company that operates the trek themselves, as they will be able to better answer your questions and will have a clearer vision of what you will experience. Don't forget to ask if the company needs a minimum number of participants on the trek--and what happens if they don't meet that minimum.
Reserve with your chosen tour operator. Most tour operators will ask for your name, citizenship, passport number, meal preferences and the date you want to begin the trek. After you register, you will have to pay a deposit of about 50 percent. Make sure you receive your confirmation in writing along with a detailed itinerary of the trip.