Some passengers step off international flights looking and feeling no worse for wear; others stagger off, exhausted and coughing. The seat you book could play a major role in determining which camp you fall into. First class is preferable in terms of comfort, of course. It's also not an option for many travelers: On an international flight, a premium ticket often costs thousands of dollars more than an economy one. It's possible to get comfortable and stay comfortable even in the cheap seats. Choosing the right one depends on your priorities – but in general, a window seat near the middle of the plane is ideal.

The Best Seats for: Sleeping

This one's common sense: a window seat is the best place to catch some ZZZ on a long flight. No one has to climb over you, and the plane wall provides a place to rest your head. Avoid window seats near bathrooms and flight attendant stations. Check which seats are still available when checking in for a flight. A window seat with an empty seat next to it is the perfect sleeping arrangement.

The Best Seats for: A Smooth Ride

Turbulence is never fun. Six or seven hours of turbulence is downright miserable. There's no way to avoid it altogether on a plane, but sitting near the wings is the best bet. That's the aircraft's center of gravity, and people sitting there should feel a little less movement than passengers sitting in the front or rear of the plane. Exactly which seats are positioned over the wings varies depending on the plane. On the large planes used for international flights, it's usually either premium/business-class seats or the first several rows of coach/economy seats that are located in the very center of the plane.

The Best Seats for: Staying Healthy

A long international flight is a perfect environment for germs to thrive in. In close quarters, sick passengers can easily contaminate others with airborne diseases and viruses. One study done by Emory University and Boeing found that people in window seats have the least contact with those germs. It makes sense; as sick people walk up and down the aisles, passengers in aisle seats are in direct contact with them. Sitting by the window provides a buffer. The other factor is that people in window seats don't leave their seats as often as those in aisle seats, again limiting their exposure. Even a middle seat is preferable to an aisle seat when staying healthy is a major concern.

The Best Seats for: Leg Room

When first class or premium seats aren't in the budget, bulkhead seats – those positioned right behind one of the walls that divide the plane into sections – provide the best leg room. Of course, that also makes them hard to get. If bulkhead seats aren't available, aim for an exit row or look into redeeming any airline points you've accrued for an upgrade to a seat with extra leg room. In most cases, the only way to get more space is to pay for it. Consider doing just that. If there's ever a time to pay extra for more leg room, an international flight is it. More space equals greater comfort, which means you're better rested upon landing. That makes it easier to shake off jet lag quickly and hit the ground running.