Americans are notorious for schlepping around various vacation destinations clad in khakis, polo shirts, Nikes and baseball hats - making it appear as if we are all employees of a TGIFridays-type establishment. While it's always important to maintain your personal sense of style, it's also a good idea to try to assimilate to the particular country or region in which you'll be traveling. Here are a few examples:
NEPAL, PERU, OTHER POPULAR TREKKING DESTINATIONS - makeup will do you no favors on the hiking trails. While trekking in the Annapurna or Andes range, if you are wearing makeup you will look like a clown next to all the adrenaline-created rosy-cheeks of other travelers. If you're feeling vain, wear your sunglasses in the photos.
LONDON - The Brits are fabulous at playing Dress-Up. Take one look at all the men in their savvy pinstripe suits, with rich purple ties, and you'll be shouting "God Save The Queen!" British women tend to take more fashion risks, and don't feel like they need to follow trends as closely as their American counterparts. This means you can try out some funkier looks: hot pants, tights and suede booties? Why not? You're on vacation!
PRETTY MUCH ALL OF EUROPE - blending in requires little more than scarves and a cute pair of flats. Those two items alone, would render even the polo shirt/khakis ensemble more palatable.
THAILAND - leave those bulky cargo shorts at home and get thee a sarong! Not only is it a chic beach coverup, it doubles as a souvenir. Many of the temples that you'll want to visit also require long pants or long skirts, and your ankle-length sarong will work.
Pack a light suitcase, and put "local shopping" on your list of things to do in the first few days of the trip. When you arrive, take note of what the cool kids are wearing. There are few things more fun than having a friend at home compliment you on an item of clothing, when you can respond "Yeah, I got it in Portugal".