The first night for most travellers coming to Peru on holiday is Cusco. It is the most well-known city in the Peruvian Andes, and in a great central situation for seeing Machu Picchu or travelling to the rainforest.
Personally though, I prefer to spend my first night in the Sacred Valley – perhaps in Ollantaytambo or Urubamba. The valley is a lower altitude than Cusco which is at 3300m. This means that you don’t suffer from such strong effects of altitude and you can slowly acclimatise. Then, after two of three night here (and visiting Machu Picchu of course), the dizzy heights of Cusco won’t make your head spin quite the same.
Another tip is to be sure that if you’re intending to visit Lake Titicaca, you keep this until towards the end of your time, as this is VERY high. Over 4000m!
Other practical tips include taking life slowly at first and not rushing around; not drinking alcohol too soon in your trip (sorry, but that pisco sour will have to wait a day or two!); and eating smaller meals more often rather than having a big blowout.
Lastly, if you’re game to try the local cure, buy some coca leaves and chew them, or drink coca leaf tea. It’s bitter, but certainly helps.
The main effects of altitude tend not to continue for too long for most people, so for the first few days be kind to your body, then you’ll be just fine.