Hi - I just finished my first sweater http://knitty.com/ISSUEwinter04/PATTmariah.html , so now on to the trick of seaming. Somethings I've read said it's really important to block before seaming but I'm not sure how critical it is and don't want to start before checking with someone with more experience.
[color=blue][size=2]The Mod Squad was here [/size][/color]
Here's an article that might help you out--I haven't done a whole lot of blocking, and I've been kind of lazy about it, but it does seem to help!
I've seamed two sweaters without blocking, and one with blocking...the blocked one was a bit easier, but not overwhelmingly so. I think the importance of blocking depends on the fiber content of your yarn, too.