I go somewhere new every few months and I’ve got packing down to a near-science. It’s amazing how little you actually need to bring, even for a multi-week trip. Besides my passport, I never leave home without:
For the flight:
-Eye mask and ear plugs for sleeping
-Ear phones and a small music device
-Chap stick – airplanes are dry; you’ll need this
-Pen for filling out customs forms.
-Water bottle – you’ll be less dependent on the airline’s service. You’ll have to buy this inside security, though.
For the trip:
-Universal power converter
-A lock for valuables. It often comes in handy.
-Toothbrush and toothpaste.
-Underwear and socks. While not ideal, I can get by with the same pair of jeans for weeks. Underwear and socks, not so much.
-Pepto bismol tablets and imodium – hey, $hit happens!
-Soap and toilet paper – not all hotels/hostels keep them stocked.
-A high quality camera and the right lenses for the trip. Camera insurance helps for peace of mind.
-Two or three weather-appropriate shirts and a pair of jeans. (check the weather forecast before you leave)
That’s it. It’s all I really ever bring, and it’s all I really ever need. All of these items should be able to fit in a standard size carry on backpack. Everything else is fluff and can be purchased abroad (sometimes for far less money than you can buy them at home).