It is a fairly simple task to get some cheap airfare to London.  All you have to do is look in the right places.  Having a flexible schedule always helps.  If you are picky about which airline you fly on, that could quickly narrow your options.  If not, then Kuwait Air or Air India should be a couple of your first choices. 

Asian flights provided by the previously mentioned airlines usually drop through London and provide cheap tickets.  Usually there is a section for US to London passengers and tend to be empty because the flights are mostly used by Asians to book a flight home.  This is a very easy way to get a cheap ticket to London.

Picking the right season can also dramatically decrease the price of your ticket.  If it fits your schedule try picking a flight between January to the end of march or between November and the beginning of December.  These are typically downtimes for the airlines.  Plan your trip during these bargain seasons if you can.

Of course, you always want to plan your trip far ahead of time.  The best prices will be for the tickets that sell more than two weeks in advance of the flight.  If you miss these early bird ticket prices then get the next best thing.  There will be tickets that are slightly above those prices that are distributed every once in a while.  All you have to do is keep checking the websites to make sure you get the good price.

Another website to try is Priceline.com.  There may be other websites like this one, but this is the most popular quoting site.  All you have to do is put in your price that you want to pay for the ticket and they will provide the service of finding the ticket at that price.  The one downfall to these types of sites is that the ticket will always be non-refundable, even if your plans change.

Be sure to sign up for any special offer alerts that websites offer.  This way you are always updated on the cheapest airfare around.