Originally Posted by littlevoices

CXFlyerBoy is entirely right, the alternative self service way, which probably isn't worth it:
1. Know that if you choose between Economy Light, Normal and Flex - the fare classes will clearly move up, but it's a bit of guesswork which fits where
2. If you have an ExpertFlyer subscription you can try and match the prices to what you are buying to work out the underlying fare class (and double check on the fare rules).

I wouldn't recommend either.