If you are lucky enough to be stuck in Terminal 5, then things are different - this terminal is brand new, and a real pleasure to spend some time. Terminal 5 is also home to the best eateries at Heathrow, including a Wagamama and a Gorden Ramsay restaurant.

Longer layovers (4+ hours)

Leaving the airport is the best thing to do if you have more than 4 hours to kill. From the terminal buildings, simply follow the signs to the Heathrow Express. The Express runs every 15 minutes, and trips to Paddington station take just 15 minutes (though in reality these trips often take a little longer). Once at Paddington, you can make your way to the Bakerloo line train, and in just 4 stops you will be at Oxford Circus. I've made this trip many times, and without delays, you can travel from the arrivals lounge of the airport to standing in Oxford Circus in 34 minutes.

The biggest downside to the Heathrow Express is its insane price - a round trip ticket is $52! There are alternatives to getting into the city from Heathrow. London Underground trains operate from Heathrow towards London on a very regular basis, the ride will be much cheaper, but it will also take a little over an hour to get to most major destinations in the city. If you have the time, this is a fun way to make your way into the city.

Once in London, the list of things to do is of course endless, and much easier to discover using one of the many London guides available. Personally I always enjoyed starting my trip at Oxford Circus, then walking up or down the street while visiting the many stores. Fans of electronics will enjoy taking a walk up to Tottenham court road, where store after store sells the latest and greatest in gadget land.

If you prefer a more peaceful way to spend your time, make your way to one of the many parks where there is almost always something fun to watch, especially in the summer months.

If you are running a really tight schedule (one hour or less) and don't mind a decent amount of walking, start at Oxford Circus, walk down Regent Street to Piccadilly Circus, then on to Leicester Square. After taking in the sights and sounds here, walk down Charing Cross road towards the Embankment and take a quick look at the Thames. Of course, the easiest way to get around is by purchasing a bus pass and hopping on board one of the thousands of buses clogging up the streets of London.

A couple of things to keep in mind before you leave the airport are of course to be aware of the time it will take to get back through security and to always keep an eye on your belongings. Like most major cities, London has its fair share of street crimes, but pickpockets and thieves are very active all around the area, especially on the tube.