Any frequent flyer can tell you that not every economy seat is the same. Some are definitely better than others. The key to finding the best seat for you is to know what's available and how to get it. Travellers are becoming quite savvy in selecting seats in advance, says Canadian travel agent Randy Raphael, who has 30 years' experience in the industry.

Seats can often be reserved when a ticket is bought and many international carriers now have online or even SMS text message check-in services available up to 48 hours before a flight, which gives passengers, especially frequent-flyer members, the chance to see what is available and make their choice. Showing up at the airport without a seat reservation can mean you get stuck with what no one else wants - or possibly worse. If the flight is overbooked and you don't have a seat assignment, you are the one likely to be left behind, Mr Raphael says. It is always a good idea to book any seat. Knowing what to pick and what to avoid is all about having the right information. Websites like SeatGuru.com, SeatExpert.com and LoveMySeat.com offer seating information for dozens of domestic and international airlines.

Seat comfort is often listed as the top priority for travellers, says LoveMySeat.com founder Steven Hall. Interactive maps on these sites provide assessments of individual seats according to their level of recline, leg room, row position, access to in-flight amenities and proximity to lavatories and the galley. The recommendations are based on thousands of user comments and industry research.

The sites also rate carriers based on seat width and pitch, which is the distance between rows. These can vary between aircraft and airlines by several centimetres, which is no small amount on a long flight. Not surprisingly, the added leg room in the emergency-exit and bulkhead rows makes them a popular first choice. Unfortunately, seats in the emergency-exit row can't normally be booked in advance because airline staff have to ensure passengers are physically capable of assisting the aircrew in case of an emergency.

Many airlines also reserve bulkhead rows for frequent flyers, the elderly or families with infants or small children. These restrictions don't mean other passengers can't get these seats, but it is one case where advance check-in or arriving early at the airport can make all the difference. These prized spaces can have drawbacks, too. Airlines use a wide range of aircraft and sometimes seats in emergency-exit and bulkhead rows can actually be cramped, not recline or are next to heavy-traffic areas near the lavatories or galley. This is where informed decision-making can save the day.

"One of the fascinating things we've discovered is that everyone has different preferences and opinions of the same seats," says SeatGuru.com CEO and founder Matthew Daimler. "While many users might complain about a seat near the lavatory, there are others who cherish such a seat because they don't have to wait in a line. "While most flyers try to avoid middle seats, we do see a fairly even split between those who prefer aisle or window seats."

A window seat offers a view for take-off and landing, and the opportunity to rest your head against the wall. And with no one trying to get past you there's the greatest chance for a bout of uninterrupted sleep. In economy class, window seats are typically the most popular location for leisure travellers, Mr Hall says. An aisle seat guarantees access to at least one arm rest, with open space to one side and the possibility of stretching your limbs a little more. This is helpful for those with newspapers, laptops, or written work to do.

For business travellers the most popular are aisle seats, Mr Hall adds. However, elbows and feet can get hit by the drink or food cart and passengers traipsing past. Those on the aisle also regularly have to move for others to get out. The least appealing option is a middle seat. Imagine it's a night flight, the row in front has reclined and the passengers on the left and right are fast asleep and hogging the arm rests. Cramped doesn't begin to describe it.

If you don't reserve your seat in advance it is highly probable you will end up with a middle seat, Mr Raphael says. For long flights this is the worst seat to have. Then there is the decision on which row to sit in. The front of the plane is usually further away from the engines and therefore quieter, Mr Daimler says. Many times the in-flight beverage and food service begins from the front, too.

Passengers at the front are also the first to get off and into the immigration and customs lines. While this can be a deciding factor for short trips or connecting flights, it is debatable how much it helps at busy international hubs. Some airlines now reserve these rows for frequent flyers. The rear of the plane is typically least desirable, Mr Hall says. It takes much longer to exit, and food and beverage service is often last to these seats. Then there is the noise and traffic associated with the lavatories and galley. Still, some passengers prefer the back because they are the first into the plane to get settled, with their carry-on luggage close at hand rather than jammed in whatever compartment is available. Then there is the little-known frequent-flyer secret of the extra space provided in the final rows of a Boeing 747, where the tapering of the fuselage means there is one less seat on each side.

Which leaves only the holy grail of economy-class seating - the empty four-seat row. Passengers keenly watch for these open spaces, waiting impatiently for the exit doors to close so they can stake their claim. Those who get to stretch out and relax on a long flight in such comfort never forget their luck. Optional extras

If economy seating is not to your liking, here's our quick guide to some of the best seats in first and business class. First class · Cathay Pacific has ranked No.1 in the Skytrax World Airline Awards (WAA) for best all-round first class service two years in a row. Seats recline into a flat bed, which is two metres long and 56-63cm wide. This year, Cathay will introduce a new, roomier seating configuration that includes an in-built massage function and 43cm television.

· Singapore Airlines has started offering a new seat - a combination seat-lounge-bed that is virtually a mini-cabin. Billed as the widest in the sky (89cm), the seat also features a 58cm LCD TV with surround sound. Available only on selected flights from Singapore. · Emirates was the first to offer the new mini-cabin seating configuration. Airbus A340-500 passengers get a 218cm x 55cm suite, featuring a massage function, personal TV and workstation. Emirates won the WAA best in-flight entertainment award in 2005 and 2006, and plans to upgrade some aircraft to a new 600-channel audio-video system.

Business class · British Airways ranked No.1 for business class in the 2006 World Airline Awards. Seats recline into a flat bed (185cm x 51cm), a feature more common in first class. BA's unusual seating configuration, which has some seats facing the rear of the plane, has received mixed reviews. Passengers get access to a travel spa at Heathrow or New York's JFK. · Qantas ranked fourth in the WAA. SkyBed seats on some Boeing 747s and Airbus A330s models have near-full recline capability (155cm x 61cm) and an in-built massage function. The audio-video system has 300 channels. SkyBeds have not been rolled out for all routes yet, with some aircraft retaining smaller seats with reduced recline capability and no power ports.

· Air New Zealand has a spacious flat bed seat on its premier service (202cm x 59cm), with a 26cm TV, remote control and ottoman footrest. Premier is available only for certain long-haul Tasman and Pacific routes.