Ok... lots of people gave you tactics... now, here's a few tactics to watch out for from the dragon.
1. And this is cheesy, but I had a DM pull this on me last year... MAKE SURE IT'S A REAL WHITE DRAGON. And not an albino vierson of another color. And just before I died, the dragon said, "Who'd expect a red dragon in the arctic? Gets me all your treasure, doesn't it?" SWIPE.
2. White dragons breathe water, make sure it's lair isn't completely submerged.
3. Something *I* pulled on a group... make sure the dragon isn't just a clone, and the real dragon is a polymorphed cohort or something.
4. Since any self-respecting white dragon knows you're be cold-buffed, watch out for it casting combat spells or a different energy type.... acid would be bad.