I made one big mistake in preparing for my Sierra Leone trip last year: I assumed $1 was $1.

Wait, what?

I assumed the exchange rates were based on the value of the dollar, and not the bill itself. I was wrong. A $100 bill in Freetown was worth about 370,000 Leones. However, if I wanted to exchange five $20 bills, they’d give me around 350,000 Leones, depending on how much haggling I wanted to do.

Before I left, I made the assumption that smaller bills would be more useful, since prices for goods would be lower. I carried most of my personal funds in $20 or smaller bills. I ended up getting burned on the exchange rates over the course of two weeks.

That kind of thing is impossible to predict, so best talk to a local before you leave. If you don’t have that option, research as much as possible on the web, with every query you can think of, even the outlandish ones.

If you’re traveling for a commercial or non-profit client, that’s a little easier, as they probably have staff wherever they’re sending you. I was lucky enough to be working for a major NGO, so I had good support on the ground. The agency paid my expenses directly, so they wired funds before I arrived, and I had a healthy amount of cash for most of the trip.

Nevertheless, things never go according to plan. On my last day, I was about $100 short of what I needed to settle my expenses. There are plenty of banks in Freetown, so it was just a matter of making a withdrawal, right? Uh, no.

I have credit and debit cards from several banks, but they’re all MasterCard or American Express. Unfortunately for me, Sierra Leoneans vastly prefer Visa. After visiting six banks, we finally found one with a sign on the door for most every major credit card company in the world. Problem solved, right? No.

Turns out you have to go to the main branch to actually pull a withdrawal from a card. Three hours later, I had the rest of the money I needed.

The moral of that story is two-fold. One, estimate high for your expenses, then add a few hundred more. Two, carry Visa and MasterCard at the very least (caveat: Visa and MC may not rescue you the way AmEx rescued me).

Pay your credit card bills before you leave, so you’ve got as much credit available as possible. Try to keep enough money in your checking account that you won’t need to move any money around while you’re away. However, balance that consideration with the possibility of fraud. Fraud is big business in the developing world, and checking accounts typically don’t offer $0 liability the way credit cards do. Check with your bank to be sure.

Cash is king. The cards probably won’t do you a lot of good on the ground, but if you need to make additional travel arrangements or change existing flights, you’ll need plastic. Also, try to find out if there are limits on the amount of money you’re allowed to bring (in or out) through customs. There’s nothing worse than stuffing $100 bills into your underpants in the bathroom at Harere Airport.

Communication

Your ability to communicate with editors, clients, friends and family depends greatly on where you’re actually going. Many places in the world have good cell reception. Some places even have Internet access.

For my trip to Sierra Leone, I rented a cell phone from Cellular Abroad. The phone worked OK most times, but it was expensive, and didn’t work when I really needed it. Luckily, my driver’s local phone worked just fine.

Since then, I’ve purchased a $50 unlocked GSM phone on eBay, and international prepaid SIM card from OneSimCard. Now, when I travel, I’ve got communication the minute I land, which is very important when your fixer is nowhere to be found at the airport. When I get situated, I’ll buy a local SIM card, and use that to make all my calls. Local cell service is almost always cheaper and more reliable, and GSM is the de facto world standard.

Depending on where you are, you may be able to purchase a cellular USB device to connect to the Web, but don’t count on it. If you’re using a Windows machine, keep it isolated from local computers. Never use a USB drive to transfer files back and forth. While there are plenty of computers in the developing world, many of them are packed to the brim with malicious software. The last thing you need is for your computer to go down in the field.

Before you leave, it’s a good idea to put together a list of emergency contacts to leave with friends, family, or whoever else you may rely on back home. You should have one person designated as your main contact in case of trouble, someone who can coordinate anything you may need. A spouse or immediate relative is the best choice: it’ll be easier for them to get information from governmental and medical organizations. You may also want to consider giving your main contact power of attorney, so they can access your bank accounts in an emergency.

The emergency contact list should be comprehensive, include numbers for your client or employer, other family members, embassies or consulates both the country you’re in, the State Department and the local American presence. You’ll also want to include more mundane things, like the maintenance number for your apartment, your veterinarian or church.

This last part didn’t really occur to me until I watched Jon Stewart’s interview Roxana Saberi last week.

Prearrange “help” signals. If something happens, you need a way to say “I’m in trouble” without saying “I’m in trouble.”

Improvising and hoping the person on the other end can read between the lines is unreliable at best.

It has to be something simple and innocuous, like asking how your non-existent dog or uncle is doing.  Discuss the signal, and what to do when it happens, ahead of time. Hopefully it’s something you’ll never use.