Let me start of by clearing a confusion most people have, Huayna Picchu and Wayna Picchu are one and the same. Every day, only 400 lucky hikers are allowed to enter in two groups, each group of 200 hikers. The first climbing time is between 7 am to 8 am. The second is between 10 am to 11 am. Make sure you reach on time as they can refuse entry if you're late. Tickets to Huayna Picchu get sold out months in advance, especially during the peak seasons, so make sure you plan it well in advance (6 months to be safe). You could book your tickets here. I was lucky to be one among the 400.The peak is about 2690 meters above sea level. The hike to Huayna Picchu is about 2 kms and has an elevation gain of about 1000 feet. It's a strenuous hike, but the views are breath taking and make it worth the effort.