When you get your bag tags, make sure that before you board your flight, stop at the gate and ask the agent if he or she can make sure your bags were scanned. It takes seconds but you'll then know right away if your bags have been loaded onto your flight. And do that again at your connecting airport.

The most reliable way to tell if your bag is checked to your final destination is to look at the baggage tag (the "claim check") handed to you at the check-in counter. The tag will list a series of three-letter airport codes. For example, if you are flying from New York (JFK) to London (LHR) to Paris (CDG), the tag should show "LHR" and "CDG". If only "LHR" is listed, you must pick up your bag in London and re-check it. Another key indicator is the "Transfer" or "Transit" status: if you are flying on a single ticket with partner airlines (like Delta and Virgin Atlantic), the bag is almost always checked through. However, if you "self-transfer" (booking two separate tickets on different airlines), you will 100% need to collect your bag and re-check it. It is also important to remember that if you are entering a country for the first time on a multi-stop journey (like flying London to New York to Los Angeles), you must always pick up your bag at the first U.S. port of entry to go through Customs, even if the tag says "LAX."