How far in advance do you need to start planning for a trip to watch the Olympics?

ASAP is the best advice. You may be able to get travel packages through international travel companies, but everything comes at a premium price. The website - www.london2012.com - will give you all the updates, but be prepared to pay a very high price to travel. Gymnastics is a premium event, though ticket prices for the earlier rounds may be much more reasonable.