First thing to do is PRAY. A lot. You need to get Jehovah's direction and blessing before you make any decisions.
If you don't know where to go, look through the yearly stats in the Yearbook. That will give you a good idea of which countries need help. Also, if you want to serve in a specific language in that country (ie English, Sign, Hindi) check out www.jw.org. Under the LOOKUP tab, you can search for meetings in different countries, to make sure they have what you want. Also, you would be surprised how many random countries have English congregations. You don't have to stay home just because you don't know the native language. But do pick up a Lonely Planet language guide. They are small, but filled with phrases you might actually use. Also, pick up sign language. Its pretty much universal.
Talk to others who have done this before. They will have good, practical advice to give you and will also encourage you with their many wonderful experiences. If you don't know anyone personally, there are many brothers and sisters who blog about their experiences and we all would love to help with any questions you may have.
Write a letter to the branch of the country you want to visit. They will tell you which congregations actually need help, and will give you the info for a brother or two to contact. Use those friends. They are very valuable for getting information about the country and where to stay. It also helps to find out where the Kingdom Hall is ahead of time. We booked a hotel next to what we thought was a Kingdom Hall for when we first got here. Turns out our hall was completely on the other side of town. Never trust Google to give you the full story. However, the brothers do have lives of their own, and are not your personal assistant. Do your own research too. And let the brothers know when you are coming, and where you will be staying initially, so they can contact you if the need arises.
Visas are not as scary as everyone makes them out to be. In general, countries like tourists because it brings them money. So send off for your visa if you need to and make sure to do it far enough ahead of time. It would be horrible to leave for your trip and not be allowed on the airplane, or even worse, get to the country and be denied entry.
If you don't need a visa for the country you are visiting, just wait until you arrive and they will stamp you into the country without much hesitation.
When it comes to renewing your visa, see what options there are for extensions without having to leave the country. Look this up before you book your tickets. For example, after your first 90 days are up, Honduras will grant you a one time extension of another 90 days for a fee. This way you can maximize the amount of time you can stay, instead of incurring the expense of leaving the country and coming back.
I also hear that there is like a 5 day grace period on getting out of the country without getting in trouble once your visa is expired. Hopefully no one has to find out if that's true or not.
Count the cost before you go. Luke 14:28 There's nothing worse than going somewhere and finding out you go through money quicker than expected due to exchange rates and eating out and just general unpreparedness.
More than likely, you are going to a congregation or group that needs help. Be prepared to be used. A lot. If you don't like answering or giving talks, here's your chance to get to like it. Step out of your comfort zone. If there's an avenue of service you haven't tried or have a hard time with, try it. You won't regret it.
Just a couple pieces of practical advice shared by a Circuit Overseer's wife given to me before we left.
First, have two blood cards. One in your purse, and one that never leaves your side. You may think “O, I always carry my bag with me.” But you don't. And that's when the accident happens. They won't know your purse is in that car parked right down the street. Your blood card won't do you any good from there. It also helps to make sure your Blood Card is in the main language of the country you are in. It doesn't help to have an English BC if no one can read it.
Second, have an emergency fund stored away somewhere easily accessible but well hidden. This is helpful in case anything goes wrong- from a strike that leaves you unable to get to a bank so you can get money for food, to an emergency bus ride out of the country due to a coup. It's always best to be prepared. Also, in the past few years, having a "go bag" in cause of disasters has been stressed in the congregations. Make sure you have some supplies to take care of yourself and your family.
If your home country has a program for travelers, enroll in it. The US has what they call the Smart Traveler Enrollment Program and they notify you of anything happening in the countries you visit. It also lets you give them information on where you are and who to contact should anything happen.
That said, the worst case scenario is not likely to happen. But “The shrewd one sees the danger and conceals himself, But the inexperienced keep right on going and suffer the consequences." Proverbs 22:3 So be prepared, but hope for the best. It'll be just fine. Don't look at all the horrible news reports about your chosen country. Most bad stuff doesn't happen to tourists. Don't get caught up in the bad news. It will only bring you down and scare you. Obviously, you want to be aware and take safety precautions, but don't let yourself become paralyzed with fear either.
Pack lightly. The old adage about packing is true. “Take half the stuff and twice the money.” If you are going to a hot, muggy climate, you probably only need one pair of jeans and a light sweater. If you are going somewhere cold, you don't need multiple swimsuits. Actually, even if you are going near a beach, you don't need multiple swimsuits. If you are going to be moving around a lot, having a ton of stuff will only slow you down and frustrate you. If you are staying in one place the entire trip, having a ton of stuff will mean your suitcase never quite gets empty and you will just feel dumb for packing so much. Most the clothes we brought, on our first trip we thought were well suited to the climate, we were wrong. And it turns out there are stores everywhere that sell clothes. So pack lightly, and if you need to, buy once you are in country. That way you can make sure you have what you actually need, and look- easy souvenir!
Unless you are going to a remote part of the country, they probably have a store with basic household necessities. If you can get a place that is already furnished, even better. However, bring your own sheets.
Don't bring your expensive jewelry. If you're married, consider purchasing a nice but cheap (Walmart) ring to wear. It's good to let them know you are in fact married, without flashing something expensive around. Also, in some countries it is not customary for women to wear jewelry, so research that before you go. You may be a visitor, but you don't have to look like one and draw unnecessary attention to yourself.
Once you are there, pray some more. You will probably have some hard days while you are on your adventure. Jehovah will get you through. I mean, bawling as you go out the door to service hard days. But he will help you make it, and you will adjust just fine.
Don't be afraid to try new foods. Don't eat fruit right from the street vendor stall, but feel free to take it home, wash it thoroughly and give it a shot. Also, look to see if the locals eat at the place you are considering. If they don't, there's probably a reason, and you shouldn't eat there either.
The best thing we have bought since coming down here was a good messenger style bag for service. Get one that’s big enough for a couple sets of magazines, your bible and some books. But don't get one that is overly large, because you will end up stuffing it full and it will be incredibly heavy by your second hour of service. Also, invest in one of those carabineer style clips that attach to water bottles. You can pick them up at REI. Hook it onto your bag, and look ma- no hands! That leaves you free to use your hands to hold the important stuff.
A couple helpful reference websites:
www.numbeo.com Cost of Living Information
Www.xe.com Exchange Rate
www.wikipedia.com Weather and cultural information
www.travel.state.gov USA Travel Advice and Warnings. Also look up the embassy for the country you choose to visit.
www.craigslist.com Helpful resource to find apartments, cars, etc
www.encuentra24.com Like Craigslist, but for Central America
The main thing is- this is a new experience. Be open to it. Don't be afraid to try new things, because everything is going to be new. Even the Coke. Don't let yourself get frustrated by the little things, because those aren't the parts of the trip you will remember anyway. Just enjoy yourself and it'll all be just fine.