hehe funny thread...
to opening poster.... good luck travelling with your friend... sounds like you're going to need it...
nothing worse than travelling with a paranoid bubble boy/girl who is too afraid to actually experience the real culture of the place you are visiting (IMNSHO)...


More on altitude: I think the most important thing is to rest when you need it, don't push yourself when you arrive and drink plenty of coca tea. There are a lot of Inca sites, museums and cathedrals to see right in Cusco, so when you get there, take a few leisurely days to explore, with plenty of time for rest. When I arrived in Cusco, I didn't feel much of anything at all. We then went to the Peruvian rainforest (sea level), and when we returned to Cusco, I did feel light-headed, exhausted and sligthly sick. We just took it easy that day, and took a long nap. At Machu Picchu the next day, I again felt a bit off, so we took a nap at a great little spot overlooking MP. Very peaceful.
We were never in a rush so we felt like we could take a nap when necessary and still have plenty of time to enjoy what we wanted to see.
There are many Inca sites, museums and cathedrals in Cusco. The best advice is to give yourself a few relaxing days at the beginning of the trip to leisurely stroll around and see the Cusco sites, resting whenever needed and drinking plenty of tea. See the Quoricancha, Sacsayhuanan, Center for Traditional Textiles, Museum of Pre-Columbian Art and whatever else is of interest.
Have fun.

Altitude Sickness: I didn't get sick on MP and don't know anyone who did but a friend and I did get woozy on Sacsayhuanan and some of the higher parts of Cusco. The guy that booked my tour recommended that I buy some altitude sickness pills to have around, and that worked fine. Once I took them I was able to enjoy the rest of my Cusco tour.
Hep A: I've never been vaccinated against Hep A and was never asked for proof of it. In retrospect, it's something I should have done but I am back at home and still alive and functioning.
Booking in advance: It depends on when you're going. June-Aug is tourist season so if you're planning to go pretty soon, it's a definite must. When I went in December, advance booking wasn't so much of a necessity because trains, buses, tours, and MP were bustling but not overcrowded.

- You must pre-book if you want to hike the Inca Trail. It can fill up as early as several months in advance.
Absolutely everything else - the train to Machu Picchu, all accomodation, all other transport in Peru can be booked at short notice when inside the country, or you can just show up.
2. Yes, take the Hepatitis A shot if you can. It is possible to survive this disease if you get it - I had it in Peru when I was a child, and the treatment was lengthy and it is a very weakening disease. Your liver can be damaged for life - meaning you can never drink alcohol again, and are almost unable to digest a few other things. The only plus of surviving the disease is that you get immunity for life. In my case I will never need the vaccine again but it's not worth getting sick for that.
3. Flying to Cusco is OK. You can get mild symptoms of altitude sickness, but nothing really dangerous. The best treatment, in case you feel dizzy and uncomfortable, is a quick bus ride to Ollantaytambo, which is much lower than Cusco and an ideal place to unwind.

hey, this is the paranoid girl writing :-) thanks for all the advice everyone. it's always good to hear what other people think. I am sure we will have a great time. and do not worry about my friend for travelling with me :-) he will be just fine and having the time of his life ;-)