I always wait until I get to know the dog's personality and choose a name that fits. Our first German Shepherd really took to my wife and instantly became her 'shadow'. Now, Shadow isn't a bad name for a black cat, but doesn't really fit a 110 lb GS. We looked up 'shadow' in a few other languages and came up with Kaja. (Japanese for shadow)
2nd GS was a freakin HUGE monster with a very gentle disposition...slept most of the time until somebody came to the door...then he came UNGLUED. I thought about it, and Greek mythology had the Titans before Zeuss took over. Story goes that they're lying dormant until they rise and destroy the world or something....it seemed fitting for a 130 lb pooch who goes from zero-to-HOLY SHIT in nothing flat.
3rd GS pissed all over the rug while eating my shoe. I started yelling, tried to say DAMMIT and got tongue tied...came out DANTE....seemed to fit! (he turned out to be my favorite)