The product manager for Quasar Expeditions, Mariana Lanusse says the key to getting the best views of the lost city is taking your time.
It is hard to avoid crowds when visiting one of the Seven Wonders of the World, however, the low season from January-March is less crowded than July, August and December, which coincide with the northern hemisphere's school holidays. The dry season from April-November is when skies are clearest over the citadel, but because it's located in a cloud forest, there's always the possibility of fog and some rain. Note that Machu Picchu never closes due to the weather (unless there are floods).
Altitude sickness usually affects people above 2500 metres. Machu Picchu sits at 2430m, while Cusco, the gateway city to this Inca site, is at 3399m. If you already know you struggle with altitude sickness, my best suggestion is to go down directly to the Sacred Valley (Urubamba) upon your arrival in Cusco. Urubamba is located at 2871m, and is a great destination to explore on your way to Machu Picchu. To avoid altitude sickness, stay hydrated, starting from two to four days prior to your ascent. Adding sugar, carbohydrates, fruits and cereals also helps.
My favourite viewpoint of the citadel is from the Sun Gate (Inti Punku), about an hour's hike up from the Inca entrance. If you don't have enough time, walk even just a little way up the Sun Gate path for great panoramic photos of the citadel. Machu Picchu Mountain is my second favourite viewpoint, the hike takes about three hours as a round trip. But, with not much effort, you can enjoy a short walk from the entrance gate to La Casa del Guardian for the classic Instagram photo. Use the windows and doors to frame those unforgettable views.
Entrance to Machu Picchu is limited: a ticket to the citadel allows you just three hours in the complex. For more time, you can purchase tickets combining the citadel with Machu Picchu Mountain, which gives you seven hours, or buy a ticket to the citadel and Huayna Picchu, so you'll have five hours. Note, tickets must be bought in advance, as they aren't sold at the entrance of Machu Picchu. See machupicchu.gob.pe
I recommend spending a night at the town of Aguas Calientes to access the best viewpoints of the lost city. The Inkaterra Machu Picchu Pueblo hotel is the best option in Aguas Calientes, while the super high-end Belmond Sanctuary Lodge is located at the entrance of Machu Picchu complex. For something comfortable and reasonably priced, el Mapi Hotel, Casa Andina Machu Picchu or Casa del Sol are all superb.
Quasar Expeditions' four-day Trek to the Lost City of the Incas tour cost from $US2400 a person (high season), twin share. See quasarex.com