its all a matter of personal preference.
some people like to do it zero...some do it 1 degree...to me, it makes sense to have some kind of bind on the driveline....if you do it at zero, it has too much 'play' and will vibrate more.
what ralph and i did on my boat was zero it at the intake where the suction housing mounts....then put the pump in....the pump shaft should be at 4 degrees at that point....then we mounted the motor at 5 degrees. we could have done it at 3, but it would have required a ton more cutting on the motor plates to get it to sit right with the rail kit (the rails were at zero)....so either +1 or -1 from the 4 degrees the pump shaft is at.