Money - make sure you take enough US dollars. The trip notes are pretty accurate, but that is just to get by. If you are a spender then take more. Change about $75 per person in the airport - the exchange rate is much better in Cusco - that will get you by for getting round Lima, the airports, water etc. When you get to Cusco change quite a bit as you will need Sols for all your shopping and eating out, only some restaurants take card. Tips for the porters can be in dollars, but you will need Sols for some of the additional trips rather than dollars.
Luggage - pack as light as you can for the Inca trail - remember the porters can only 7kg of what you will need and some of that includes your sleeping bag and thermarest. Make sure your sleeping bag is warm enough - work on the comfort rating rather than the temperature rating. A two season bag is not warm enough! You will need more tops in the rainforest than you think as you will need to change at least 3 times during the day, where as on the Inca Trail you probably don't need as much as you think! And if you do, remember you have to carry it!
Poles - if you are used to walking with poles, take them as they help with the ups and downs. If you are used to walking without them, then you probably don't need them - you can always find a sturdy stick en route.
Water bottles - take bottles that can be filled with boiling water as these can be used as hot water bottles at night while camping.
See if you can get the earlier flight back from Puno to Lima as we had to hang around for 5 hours after getting back from Lake Titicaca before the 9.00pm flight to Lima and couldn't see any reason for this. It means you don't get to the hotel until nearly midnight!
Enjoy the culture - each town has its own square and cathedral - from the poor to the rich, enjoy the wildlife including macaws, sloths, condors, caimans, monkeys, parrots, snakes, spiders, etc, etc, and enjoy the ruins, as I am sure that's why you will book the trip in the first place.
Try the alpaca - very tasty, guinea pig - not much meat and a lot of little bones. If you like tea, make sure you have the coca leaves, but if where you work perform random drug tests, make sure you tell them you've had some, because it stays in your system for a week after you get back. If you are not sure about antimalaria tablets - we took them - check your insurance, because if you do get bitten and get malaria your insurance may not pay out!
Be prepared for the travelling, but just do it as it is out of this world!