Don' go to websites that talk about it
And ignore anyone talking about it 
I agree 100%. The week before a Harry Potter book comes out, I avoid pretty much all Harry Potter related websites because I'm afraid of spoilers.
Horror-ish story: when the 6th book came out, I was at Borders standing in line to pick up my copy of
Half Blood Prince, when suddenly this guy bursts through the doors, shouts, "RON DIES!" and then runs away. The whole room went reeeeally quiet. I was so angry. Fortunately, after reading the book, I realized he was just making it up. But if anyone does that again this time, I'm going to hit them over the head with my copy. And then perhaps I'll cry.