London Euston to Olympic Park

Elvisia

or Euston Square to Liverpool St and then a few stops on the Central Line is another option.

vivatifosi

Another vote for the Javelin here. Not only is it quick and convenient, its worth saying how luxurious it is compared to the tube!

It's also worth mentioning, that if you live outside zones 1-9, you can get the Olympic train tickets which work out pretty cheap as an add on. You use them to get to Euston, then use the Paralympics travel card on the Javelin. You can also upgrade to first if you want total luxury. Train to Euston, walk to St Pancras and then the Javelin to Stratford was only an hour in total.

SimbaSimon

Another vote for the Javelin for your route. And yes, unless you fancy a 20 minute walk avoid the advice to go to West Ham. Never had to wait more then 10 minutes for the Javelin and the queues were always moving.