Replacing belts

I went to try to replace my belts today on my 99 GLE and was suprised at what a pain it was. I adjusted the tensioner, but no matter which direction I went with it, I couldn't get enough slack to take the belt off.

Any tips for me? I don't feel like paying a mechanic to do it for me.

Come on guys, I know someone has replaced there belts out there.....