I try not to judge books by their covers, but I will admit a pretty or interesting cover helps. If I like the look of a cover, I'll often read the back or inside flap then to see if it would be something I'd enjoy. If a book doesn't have an interesting cover, but I've heard great things about it I'll still pick it up. For instance, I don't like the covers of the Vampire Academy series but I've read great reviews of the books so I started reading the series...and I loved it.
Don't forget to enter my giveaway (here) for a chance to win a copy of Clockwork Angel.