Well, to cut to the chase, when ever you decide to, you criticise the world around you. I know this sounds like the normal method, but you take it to the extreme, i.e thinking "Surely that isn't possible" even when it probably is.
e.g You see a bird, and think "I must be dreaming, that bird is floating!"
and when you see a person you could think "since when have humans had two legs? I must be dreaming!"

This is in the earliest stages but I thought I'd put it in testing area, so please reply, preferably after trying the technique!