kew1 saidTickets go on sale in 2011 (no date yet) .Fake websites offering tickets already up & running. london2012.com
yep, the official website will give you information on official ticket agencies in your country, and how to order.
I don't recommend going through travel agencies for tickets either, as they will be several hundred percent more expensive than the official ticket price.
some tickets for popular events may be difficult to get, so try to order different sports.
you probably don't get all the tickets you want. But I went to Beijing with tickets for just one event. And I was still able to get tickets for what I wanted to see.
I met a hardcore olympics fan from Canada, who'd been to every olympic since 1984. And he'd never bought a single ticket in advance. If you only need tickets for yourself, just go to the venue well before your event starts.
there's almost always someone (other tourists/sportsfans) w a spare ticket who'll sell it to you at face value, or a reasonable price.
there are scalpers too, but just turn their ridiculuos prices down. Sometimes they can't sell their tickets either and become desperate as the event is about to start and they'll drop the price. Learn the official price, and decide how much YOU want to spend on a ticket.
I got 6 tickets like that, and the most expensive one, was only double the official price. One of the tickets I even got for free (I visited a local judo club and practiced with them. then they asked me if I wanted a ticket for the judo venue... sure why not LOL)