Get thee a bead jack:
http://www.amazon.com/Kool-Stop-Tire.../dp/B001AYML7K

Silly looking tool, but works like a charm on tough new tires. I've never figured out the trick. On the road, I have a VAR Tyre lever. Some day that is going to break and I'm going to be in trouble.

But, for changing tires at home, the Kool Stop bead jack works like a charm even on tire/rim combinations that the bike shop said would be a PITA to install.