Sign up for frequent-flyer programs. Almost every major airline has a frequent-flier program where members earn points based on how far and frequently they fly with that airline.The more points you have, the more loyal you are viewed by that airline, and thus more valuable to them. Be sure to sign up with the frequent-flier program of each airline you fly. The more points you have, the more likely the airline agent will assign you bulkhead seat.
Pay a fee for a bulkhead seat. Many airlines charge more for seats with extra legroom, including bulkhead seats. You can pay an additional fee, from $10 to $50 each way, for a bulkhead seating. Most airline websites provide the option of changing seat assignments, so after you buy your ticket you can check online to see if bulkhead seats are available to purchase.
Get to the gate early. Frequently seats with extra legroom are assigned to passengers on a first-come basis after they arrive at the airport. If you get to the airport at least two hours before your flight, you will have a better chance of getting one of these seats.
Spend a little extra time being nice to the ticketing and gate agents. These people are really the distributors of the extra-legroom seats, so approaching them in a courteous and respectful manner could go a long way toward a choice seat assignment.