1. Bank strategically.
Opening a bank account in your new home might be a real pain in the ass. Especially if that new home is in France. Or maybe you won't be staying put long enough such that it's worth the bureaucratic hassle. Accessing your funds from overseas without racking up huge fees can be rough, but certain banks are more helpful than others. Bank of America, for example, is part of an international alliance that lets you withdraw cash from ATMs without paying fees - BNP Paribas in France, BNL Italia in Italy, Barclay's in the UK, Westpac in Australia, etc. I've heard Charles Schwab waives foreign transaction fees. And credit card-wise you can't beat Capital One - they don't charge foreign transaction fees and you can easily set up travel notifications online so your account won't be blocked when you swipe your card overseas.
The downside is that very few American banks have cards with smart chips. This was a huge problem for me in Scandinavia, where I found my cards repeatedly declined. Luckily my travel buddy was there to bail me out and I repaid her later in cash.
2. Get your prescriptions filled early.
It is possible to stock up on months' worth of your prescription medication, but generally that requires a special call to your insurance provider. Another thing to consider is how much space your stash will take up when packing. A single pack of BC might not seem like a lot, ladies, but when you have dozens that's not so much the case.
3. Verify whether you'll be needing a visa and how long the application may take.
This might seem like an obvious one but consider my friend who was once stranded in Atlanta after being unable to board her flight to Brazil on account of not having a visa. I know, I know, Americans don't need them for many places but it's much better to err on the safe side. Some, like Turkey or Australia, can be purchased easily upon arrival or online ahead of time. Others, like India, require an actual application.
4. Get immunized.
Allow enough time for this because some require multiple shots that could be spaced as far as four weeks apart. Tell your travel doctor where you're going and they'll prescribe you some medications that are useful to have just in case.
5. Back up everything in every place imaginable.
Carry extra copies of your passport and visas. Scan them and email them to your family. Save them to Dropbox and Google Docs. Do the same for your travel itinerary.
6. Unlock your phone.
Oh, wait, that's illegal now. Well if you hopped on the bandwagon before the government got involved, purchasing foreign or international SIM cards for your smartphone can save you a lot on the road. (Nothing is worse than roaming data charges). If you'll be going to a lot of countries for relatively short periods of time, SIM cards from the likes of Telestial, OneSimCard and Doodad are probably best. If you're staying for a while, look into purchasing a local one at the airport - but be careful, sometimes it takes confirmation from your hotel/host before they hand over your new SIM card.
7. Eat like a pro.
Leaving home you'll probably find that the likes of Yelp and Urbanspoon, which collate reviews from users, haven't percolated throughout the rest of the world. Yes, there's always TripAdvisor, but they have a bit of a bad rep when it comes to fake reviews. And, yes I am kind of a food snob, but the masses don't always have the most discerning palates. So it's best to follow the local authorities. In Paris, for example, I relied on Paris By Mouth, which is curated by a group of experienced food writers/editors. For more general traveling and eating (especially street food) tips check out Legal Nomads. Tyler Cowen's Ethnic Dining Guide has good tips for stateside visitors. I also like Where The Fuck Should I Go To Eat. But no matter where you are, chances are there are plenty of local food bloggers with useful insider information.
8. Learn how to shit properly.
I mean it. If you're going to a developing or rural area - especially for the first time - you would do well to memorize this book. It can be redundant at times, but I guarantee you'll learn something from it. (Luckily I never had to resort to using squat toilets, but thanks to Dr. Wilson-Howarth, I know how to if the need arises!)
Got a friend of a friend or a distant relative in the area that you're visiting? Don't feel awkward about reaching out to them. Even if you just end up meeting up for coffee and not staying at their house, having a local contact is invaluable. Say yes to every invitation, because you never know what could come of it. Like that time I went to a dinner party at my friend's house in Delhi and met the co-director of Slumdog Millionaire.
If you hit it off with your Airbnb or couchsurfing host, stay in touch. You never know when you might be able to return the favor or, maybe, the next time you visit they'll let you crash with them free of charge.
10. Document it.
Particularly if you're on a long trip, you need some way to organize your thoughts and memories, whether it's public like this blog or private like the journal I kept whose privacy was violated by an Australian customs agent. I thought I made a good effort, but even now I find I get people, conversations, locations mixed up. There will be no end to new experiences, so keeping them all separate is the hard part.