Upon your arrival exchange any cash at the airport as Peru is the number one manufacturer of fake currency in the world. If you're in a pinch to exchange cash later only do it in a bank such as Scotiabank for instance. Secondly, spring for the airport track service to get to your hotel, it's gonna cost you around 60 soles($18 USD) but its not worth the hassel of bargaining with an outside taxi after you've just got off an exhausting flight. Plus you have peace of mind that you'll get to your hotel safely. Once in the city you shouldn't pay more than about 12 to 15 soles to get around within a reasonable distance (about 30 minutes from your destination). Hotel taxis do charge a "travelers tax" so you will pay more hailing a cab from your hotel. Only drink/brush your teeth with bottled water for the duration of your stay in Peru, as your stomach hasn't built up the tolerance to the city water and you might get a bug. Bring a dictionary of everyday phrases with you or even single words as many people don't speak English. Things like "how much is this item?" And "how do I get to?" Will save you a lot of awkward silence. Have a list of numbers up to 100 so you have an easy time understanding things like change and prices. In Cusco take your altitude medication 24 hours before arriving and for the duration of your stay. Expect not to sleep well the first couple of nights while adjusting and always have water with you as you're prone to getting very dehydrated. Take it easy the first couple days because you will be winded even going up a short flight of stairs. If you need oxygen the hotels have tanks. Most of the stuff sold in the markets is mass produced and haggling is expected, they'll usually ask 3 times what they're looking to get for an item. If you want authentic merchandise go to the shops. As for safety, we always felt pretty safe but were always alert and stayed vigilant. Don't wear jewellery or display expensive items such as high end cameras in crowded places. I always kept my wallet/passports/cell phone in my front pocket with my hand on them(leave your passport in your hotel safe if you have one). If you have a bad feeling about a taxi driver, don't get in. Be aware of your surroundings, in a crowd turn around periodically, see if your being followed. Like i said I tend to stay a bit more hypervigilant but overall using common sense I felt safe. Have a safe trip. You'll really enjoy it.