Taking an overseas assignment can be a great career boost. However there are some major issues that you need to consider.
Taxes will heavily depend on whether you are on an "ex pat assignment" (you are still being paid by your employer outside of the US) or whether you are on a "local contract" (paid by the company locally in Australia). Likely an ex pat assignment contract will already include provisions for your US taxes as well as the local taxes you will owe in the other country, but a "local" contract will only consider the taxes you will owe to that country. The US is the only country in the world that taxes their citizens on their WORLDWIDE income. So even though you may earn every penny in other country on your local contract, the US wants to tax you for it. Fortunately there is a "foreign earned income tax" exclusion that you can apply for that will prevent the US from taxing you for the first $80,000 but above that value you will be taxed by both countries. Furthermore, to get this exclusion you have to meet certain rules, the first and foremost being that you can only be in the US for 35 days/year. So if your employer plans to send you back to the US for business, get them to write provisions into your contract regarding the number of days of travel in the US - or get them to write in the contract that they will pay the excess taxes if you go over the 35 days.
You should talk to a tax accountant familiar with ex pats and people working overseas as they will be able to provide you with tremendous information and advice. There is a lot about this on the Internet (there are lots of ex pat websites that give advice about everything) prior to negotiating your local contract.
Keep a local US address - find someone in your family who you can have all of your mail forwarded to and whose address you can use on your US tax forms.
We recommend that you negotiate into your employment contract that your company pays for a local tax expert to do your non US taxes every year you are there; if you are on an ex pat assignment, ask for them to pay for doing your taxes in the US as well. The laws and rules in most other countries are different than the US and making them pay for an expert will save you time and money; it is a vital part of taking an overseas job.
The US requires that if you have a foreign bank account every year you must file a form with the Treasury Department to list all the foreign bank account numbers you own. This is all a terrorism check but if you don't file it, you can go to jail - so best to file. Ask you tax accountant about this, as this is quite important.
Foreign branches of banks do not talk to their branches in the US. For all intents and purposes, they are totally different banks. You can wire money back and forth between your accounts (with associated fees), however it is easier to live with the separate accounts. Bring enough money (cashier's check, ATM funds, and cash on you) to get started; plan on extra money as a safety net for things you did not plan on or expect (potentially a few thousand dollars). The bank will take about 2 weeks to clear your cashier's check. Visa/MasterCard/Amx work everywhere and are a lifesaver. Set all of your bills and banking up for on-line banking and bill paying - it will save you time and effort and give you full view access to your US accounts from far away.
Paying your bills in a foreign country is not at all like in the US and arranging for car and home/fire insurance can be a challenge. Be friendly when you arrive and try to build a network of people who will help you figure this out.
The US tends to move people based on the weight of their goods, but overseas most will do it based on volume. Have your movers come and estimate the volume of your household goods and then you get a feel for how much will fit in a new "smaller" place. You should ask the mover's if they will move food, spices, wine, or alcohol. We have heard of some ex pats (especially those with kids) whose movers would move food and the packed literally boxes upon boxes of cake mixes, mac and cheese, etc. You should box up things like you favorite hair products, soaps, and facial products. Just put it in a box labeled books and the movers did not ask any questions. The best thing is to find out exactly what they will NOT move up front. We also suggest doing a major purge of your house before the move. Most apartments/houses outside of the US are not as big or spacious as we are used to - so you will have less room to work with.
When some people open boxes with blankets, clothes, and sheets, they smell weird. Be prepared to do a lot of laundry and dry cleaning those first weeks after getting your goods. Just be prepared as this is something most people do not expected.
If you plan on coming back to the US, might leave any valuable goods (antiques, paintings, etc) with your family. Boats have been known to sink; containers have fallen off ships in bad weather, and while these items are insured, they could be lost forever.
Leave most of your electronics in the US. Your TV, stereo, microwave, washer/dryer, blender, even alarm clock, hair dryers, and telephones will not work on the power in many foreign countries. Accept the fact that you will need to buy these goods locally and sell them before you come back to the US. The one exception is a DVD player - note your US DVDs will not work on an foreign DVD player as your DVDs are coded for the US (region 1). For example, Australia is either region 2 or maybe even region 3. You can buy a "universally coded" DVD player at Best Buy/Circuit city, but it will still run on 120V power (maybe they now sell one that will run on 240/60). You can buy a "step down transformer" that will have a US plug on the front and the transformer can plug into the wall with the right plug. See exactly what type of plug you need - the UK uses a giant plug with angled pins. We suggest buying some of these step down transformers and a handful of "adapters" for any electronics you have that already accept 240V/60Hz (laptop, iPad, palm pilot - just check the requirements on the device. Do some Internet searching to find the exact electrical requirements in country you are moving to.
Your goods will take 6-8 weeks to come from the US by boat - so be sure to negotiate into your contract that they put you into temporary housing or a hotel until your goods arrive and provide you with a car. Ideally get them to hire a relocation service to assist you in finding an apartment/house when you arrive, as a local who knows the area will help you a lot with all of the rules/laws/contract differences from the US. Leases work differently in every country, so help like this is valuable. Also, search the Internet for an foreign countries' ex pat website. The information on that website will be specific to that country and the tips will help you immeasurably. The Internet is a great way to learn about what is coming your way so you can be prepared.
Car and Driving
It is not cost effective to ship a car. Sell your car and buy a new one in your new country. You can read on the Internet that getting your US car imported into another country can take a lot of time and be costly if you have to have special local requirements implemented on your car. For example, Belgium would have required that your speedometer be predominantly in kilometers and not miles, a special fog light setup may have to be installed on a US car, and emissions testing performed. All of it not worth the hassle for your typical US car. Check the laws for importing if you are moving a car though.
Buying a car locally - ask how this goes from your colleagues and friends. From the day you sign the paperwork to buy a car to the day you can drive it off the lot, can take up to 3 weeks in some countries. You paid the money for the car after week 1 and still waited 2 weeks for the licensing and insurance to get sorted out before you can drive the car. Every country is different. Most people naively assumed it would be the same as in the US and ended up paying 3 extra weeks for a rental car that they did not anticipate or budget for.
The US does not use the "international road signs" so you can find these on the Internet and study them before you arrive. You will may have to drive on the "wrong side of the road", which is not hard, but it does take some getting used to. Try to get your hands on an foreign countries' driving manual before you arrive as the rules of the road are different in almost every country. Things like stopping and going at stop signs or lights are the same, but in many countries there is NO right turn on a red light ever! Also cars entering the road from the right always have priority over the main road UNLESS you are on a road with an orange diamond sign which means that the forward going traffic has priority. HOW CRAZY IS THAT??? Welcome to living overseas. . . weird rules that you as a foreigner don't get and would never guess. This is why a driving manual is very important.
Getting a work permit, temporary resident's visa, your driver's license, and local ID in foreign country is a paperwork frenzy. Get as many of your personal documents together and organized up front (birth certificate, passport, immunizations, etc). Go to a passport photo shop or Kinkos and get like 20 photos made - almost every document in foreign country required a passport sized picture to be attached to the papers. Many work permits also required doctor's "statements of my health" (both mental and physical), a tuberculosis test, a criminal history document from the US law enforcement, getting fingerprinted on special cards and sending them to the FBI to get your federal criminal history.
Lots of paperwork and little costs; things that will take you away from your job in the busiest weeks before you leave, so be prepared. Once you get here, it does not end. The local bureaucracy begins. It can take many trips to the city hall to get your local ID card and your driver's license. You will typically have to go back yearly to renew your work permit and residents card. You may have to forfeit your US driver's license to get a foreign driver's license. It would be a good idea to go to the DMV and get a replacement before you go. Tell them I lost yours and got another one (the address should be one that you know will be able to get mail at while you are out of the country). Keep all of your receipts as these are often reimbursed by your employer and can also be used as moving expenses for your tax preparations.
When you arrive in the foreign country typically you know virtually nobody. It is critical that you find a group of people soon after arriving. Type "Americans (country name)" into Goggle and find some local groups. These groups help you to meet other Americans who are in my exact same situation and who have already crossed the hurdles that you are just going over. These clubs often have "Newcomer" events that will welcome you to the area or subgroups (e.g. American Rotary, Mothers of Young Children, Retirees, Working Women's Group, etc) that will help you almost immediately find other Americans in similar situations to yours. These are a great resource for meeting people, getting answers to your questions, and making friends. The nice thing is that these clubs do a lot of social events and it is a good introduction to the area and to some of the cultural aspects of your new country. These clubs will also sometimes arrange travel tours, which can be a lot of fun.
The reason why it is critical you find people after you arrive is that you will go through a major case of culture shock and homesickness, in waves of strong to weak, for the first year. New job role, new home, new country - it will all build and be overwhelming. Culture shock will happen. Foreigners will simply do things differently than you have ever done them and you will think it is freakish and weird. Early on, everything you do will feel like going over a hurdle. Going to the grocery store was a major hurdle - as all food is written in a foreign language and is in metric measurements. It takes time to figure things out - accept that you will make mistakes and try again.
Just be aware that it will happen, even when the language is not a barrier for you. It is normal - find your network of friends - and they will help you figure out your way through the maze much faster.
There is a series of books called "Culture Shock: (Insert country here)". If they have a book on the country you are going to you might buy it. These are good because they discuss a lot of the cultural differences that you might not be aware of (and there are many!!!). Look on Amazon, I am sure if it exists, they have it.
Have a power of attorney and a will before you leave the US. Have an the attorney look into what could be done to make these documents legally recognizable in the foreign country. It costs more, but you know that if you die tomorrow, someone is legally setup for helping get you returned to the US for burial and to take care of all of your financial assets/debts. This makes a lot of sense and will make it easier for your family, god forbid, if something happens. The only thing you cannot setup is a living will. These are only recognizable by state and are not internationally recognized. You could write one for the country you will be in, however most people have one written for a state in the US that clearly states what they want to have happen if they are in a horrible accident and decisions must be made.
This is a guideline for your family and a statement of your wishes to limit questions should something happen. We also recommend that you ensure that beneficiaries are in place for all of your accounts and financial assets. It will simplify your estate if something happens.
Renting your Home in the US
If you do this, I you should find a fantastic property management company that does background checks (criminal) and credit checks on potential renters. Also, get the highest end rental insurance and fire insurance you can buy with replacement cost adjusted for inflation.