One advice don’t book in advance unless you want to do the Inka trail which I think is way over-priced. Again, if you are only going on a short holiday you might just want to threat yourself with the most popular trek in the world (quite possibly). They are alternatives to this trek and the second best option if you are an avid hiker is:
THE SALKANTAY TREK
This trek literally means ‘Savage Mountain’. The beautiful hike will start in the mountains by a beautiful mirrored lake. On your second day you’ll walk up the mount Salkantay glacier. On the third day, climate will get warmer and you’ll be walking to a tropical forest. On the fourth day you’ll keep trekking the jungle and if you’re not afraid of heights you can do some zip-lining. You’ll spend your last night in Agua Calientes, which is the travel hub to Machu Pichu. Finally on your fifth day you’ll walk up to the spectacular Inca city.
THINGS YOU NEED TO BRING WITH YOU… some winter and summer clothes, good hiking shoes, sunscreen, swimsuit (there’s some hot baths on the way), insect repellent, torch light, water bottle or water pouch… All the tour groups operator will carry all your stuff so you don’t have to worry about hurting your back, just take a smaller day pack to take with you during the day.
Cost: $180 (US dollars) for 5 days 4 nights trek
If you are really really good with directions and a big adventurer, you can do the Salkantay trek by yourself. You just need to carry all your stuff with you at all times along with a map. TO be fair you could just follow all the other hikers doing the tek.
THE JUNGLE TREK
If you are not big on hiking no problem you can do the young, fun, adventurous JUNGLE TREK. This journey to Machu Pichu lasts 3 days and offers mountain biking, rafting, zip-lining and a little walking. Great if you are not a big walker and want a 'younger' option. This trek usually attracts younger crowds so it's just up to you how young you feel at heart :)
Cost: +$200 onwards
I would recommend going up the mountain in machu pichu it’s about $5US extra on top of your package. It’s a bit of a trek uphill so you need to be reasonably fit but the views are worth the sweat. Also, Machu Pichu gets crowded very quickly so it’s lovely to be up there with only a few others. I would also recommend booking the earlier slot to go up the mountain as it can get very hot later on.
If you are well organised you can book Wayna Pichu which is a smaller mountain with ruins and a butterfly sanctuary. To guaranty you a spot up there, it’s recommended to book months in advance.
Apart from the Inca trail all the treks can be book days before. Generally in SA, it’s cheaper to book once you are at the port destination or you’ll be likely to be charged triple the price.
Also if you want to save a bit of extra cash you can take a bus back to Cuzco instead of a train. Nevertheless, this will mean that you’ll have to leave the ruins earlier and walk an extra couple of hours! It’s a good option if you are on a big trip as every pennies count, hey?!