Choose A Venue
Consider which events you will be attending - The various Olympic events are spread around, so you should consider where the venue is that you will be attending and, for convenience purposes, attempt to book a hotel which is either in the area or has good links to it. Planning ahead could save you a lot of time and hassle. If you are staying in central London, try and grab a hotel near the venue you have tickets for, before they are booked out. Consider attending also the idea of attending an event such as the Olympics football in Cardiff and Newcastle. Tickets and accommodation will both be much easier to acquire.
Check for cancellations - If, as the games approach, you find yourself still without accommodation, it is worth ringing hotels on the day that you require accommodation in order to see if any cancellations have been made. You could even request to go on a list to be contacted should cancellations be made. Also you might want to dig out that old address book and befriend some of those people you haven't talked to in years and who live in London.