Went there 3 years ago. Stayed in Lima for a few days...not a great introduction to an otherwise beautiful country, but is an eye opener and a real experience
Then went to Puno and Lake Titicaca. Lovely area (the reed islands were fantastic, if a bit touristy...Taquile island was beautiful)and did'nt get any altitude sickness despite all the warnings you hear.
Got the train then to Cusco which was an amzaing 10 hour trip through the mountains
Used Cusco as a base for Machu Picchu and the surrounding areas. The hiking and day trips, excluding Machu Picchu itself, are well worth going to Peru for alone. Inca trail was booked out but did'nt have 4 days in any case to spend on it.
Walked up to Machu Picchu from the town at its base and got there at dawn before the tourist buses arrived in. tough climb but there's a good path zig zagging up the mountain side
Was there in September time and it was hot in the muntains without being unbearable. Great value over there. lovely people. Would go back in the morning and hope to do so again someday