1.) Dust is everywhere in Lima and some other places (Nazca!). Lots of it. Your fingernails will always need cleaning. Take a small nail brush.
2.) Save your soap slivers at home and toss them into a baggie for this trip. You can break them into pieces and have enough to use in a public bathroom by tucking one or two into a pocket each day. Just leave it there after using or toss in the trash. Soaps from hotels are great for this, too. This is also handy for showers in various towns where you don’t wanna waste a new full sized bar. (Thanks Cara!)
3.) Sunblock is your friend. Get a small container to carry. High SPF’s are a good idea. Sweat-proof (ha ha ha) is also a good idea. Don’t forget to use a hat.
4.) It is noisy! Drivers honk to indicate their location in relation to other vehicles and to pedestrians. They also seem to honk for entertainment.
5.) Hot water. It is a luxury. Most people shower cold or with an electrical device that is a showerhead. I never saw one that sprayed well.
Don’t. Touch. This. While. Showering! It. Will. Hurt!
It is not uncommon to see a light switch actually in the shower of a hotel or hostel.
6.) For laundry, bring a bar of washing soap or some liquid. If you are using powder, you might wanna put a small amount (1/2 cup?) into your blender and grind it into the finest powder possible. (Wait for it to settle to take off the lid or pour it outside so you don’t breathe it.) Plastic clothes dry much, much faster than cotton–nylon, rayon, polyester. Practice hand washing in a tiny container while at home so you have the skill already when you need it. Travel books describe laundry services as being everywhere. This is a lie. If you are traveling to a new city every 2 days, there isn’t enough time for your jeans to dry on the line used by the lady you pay to do your laundry. Be prepared. (You can take one pair of jeans and buy some cool pants made from Peruvian fabrics as a souvenir/useful item.) A place to hang something in a hotel shower is a rarity. And the humidity in the shower area prevented what I did wash from ever drying. We did pay one day for laundry after 11 days. (I had hand washed my underthings and they were still wet after 2 days.) It was 10 soles for 2 kilos of clothing in Cuzco.
7.) Women – I recommend that you take a sarong. It is multipurpose and very handy. I used mine every single day. (Emergency towel, cover, skirt, shawl, etc)
8.) Cheap flip-flops. Use them in the shower and everywhere when you are not in your regular shoes. The floors are almost always tile and super slippery or super dusty/dirty. Make sure they fit together in a Ziploc. If you have any of those silica moisture-absorbers, this is a good time to throw one in.
9.) Pepto Bismol. Bring it. When you need it, you don’t want to have to look for it. It can be difficult to actually locate it in the pharmacy. It is always behind the counter in Perú.
10.) Take plastic bags for vomiting. I am serious. In the very least, always have a couple of gallon Ziplocs available.