Travel is always easier if you know before you go! The challenge of course is that we don’t know what we don’t know! I always try to provide a great deal of info to my clients when they travel, but sometimes there are things I consider so “routine”, that I may not mention if not asked. Let’s look at the basics of leaving the US and re-entering the US on flights.
Something to know before you go is that you will have to meet the entry/exit requirements of the destination. Some destinations have very stringent requirements when it comes to criminal history. Regardless of whether you have a passport or not, there are certain criminal histories such as felony (or even some misdemeanor) convictions that will deem you ineligible to enter their country. Being behind on child support is another issue in many destinations. Please, do yourself a favor and discuss this with your travel professional prior to booking or traveling. Trust me when I tell you it is an awful phone call when someone has been denied entry to another country.
Speaking of passports, your passport must be in relatively good shape. It cannot be damaged, separating, missing pages, or anything. These types of things can deem your passport invalid for travel.
Something else to know before you go is that on the flight to your destination, the flight attendants will pass out immigration and custom declaration forms for you to fill out. These forms must be filled out prior to passing though immigration and customs in your destination. The forms will require your passport information, address (or name of resort) in destination, and your departing flight information. It will serve you well to keep your itinerary and passport within reach during your flight, that way you aren’t scrambling to get the info or trying to fill out your forms while walking to the immigration line.
Upon arrival in your destination, have your passport and forms handy. You will need to provide them to the immigration offer. They will sometimes ask you a couple of questions, most often they ask what is your purpose for the visit and how long are you staying. They do this while they are checking for any “flags” on your passport. (This is where my advice above about past history can come up) Some destinations will provide you with a tourist “card”, often just a piece of paper, upon entering the country. Do NOT lose this….
Once you have passed through immigration, you will proceed to the baggage claim area. You will need to pick up your luggage at the conveyor belt and then head to the customs lines. Your baggage is often screened by an x-ray scanner and / or hand inspection by officials. Once you have cleared customs, you are on your way to the vacation you have been waiting for! Just a note – in many countries, time share sales are very aggressive in the airport. In Cancun for example, I tell people once you have your bags, head for the double doors as quickly as possible. Do not make eye contact or engage in conversation! The time share people will have very enticing offers to get you to listen. Do yourself a favor and don’t. Head to your pre-arranged transportation and start your vacation!
Sadly, all vacations come to an end.
If you are in a country that gave you a tourist “card” upon entry, you will need to present that when exiting the country. Do not lose this; you would not believe the headaches involved for losing a 2 x 2 inch piece of paper in some countries! Some countries also require an exit “tax” to be paid. It often has to be paid in local currency and cash only.
On your flight back to the US, you will be given customs forms to fill out to re-enter the US. Again, you will 
need your passport and flight information, so keep your passports handy on the flight. Once you land, you will proceed to immigration. Many airports in the US now have kiosks which have really helped to speed up the process. Of course I always recommend Global Entry! Global Entry takes all of the hassle away.
If your first airport arrival in the US is your home airport, after customs you retrieve your bags, proceed through customs, and head home. If your first airport is a connecting city for you, you will retrieve your bags, proceed through customs, re-check your bags, proceed back through airport security, and on to your gate. As a note, if you purchased any beverages or liquids in one of the duty-free shops over the carry-on allowance, you will not be able to take it through security. You will need to pack it in your checked bag before re-checking your bag.
I hope this has been helpful! Remember, we don’t know, what we don’t know, and it’s helpful to know before you go!
Happy Travels!
Kelley