I would recommend having some hours (approx. 15-20), just to experience the airborne environment. I concur with LJR in the fact that knowing why runways are numbered (for example) gives you a little more brain space, as well as being familiar with radios and R/T.
I came from the 0 previous flying hours school and struggled through Basic GF (equiv. of civ. GFPT). Later on down course though it all becomes even par when you get into nav and form etc.
I really came unstuck on initial emergencies such as engine failures as i had very little idea of how they should be run. I had seen the insturctor demo them previously once or twice, but when it all came doen to him pulling idle with the dreaded words "practice", the demo he had previously given me seemed a world away. I remember thinking that I was having enough problems doing R/T etc and then he pulls this stunt on me! '
I think with some prior flying experience i may have been more comfortable with some of the basics and would have made the rest a little easier.
But if you do come from the zero hours club, don't worry, there are plenty of us who passed doing exactly that!!