It could also be a good idea, if you're on your own with no chance for a spotter or a trainer, to video tape your lifts and post them on a forum (I suggest this one, for instance: http://www.crossfitbrandx.com/index.php/forums). Will allow other nice people to comment on your form and give you tips. Plus, if you're doing something massively wrong, they might be able to spot it.

I've also found that if you ask other people who look like they know what they're doing at the gym to show you stuff, they'll be more than happy to. You do run the risk of being shown wrong though. I'd double check with youtube afterwards.