The whole prep thing is really the difference between a professional background, or at least a professional attitude about your photography and an amateur one.
So coming from that background, I have learned to do a huge amount of preparation before I go out to shoot.
For those who do photography purely as hobby or passion, the pressure on them, both financially and emotionally, is less.
This has been an interesting thread. For me, how much luck plays into photography is a distinct: "maybe". When I was shooting weddings, or other editorial work, I was prepared and did all the things I thought a pro should do to ensure a salable produce, just as Brian said.
But, for the rest of my photography, I am pretty much an amateur, and so all that goes with that classification tags along with me most of the time.
On the Texas Church Project, we started as no more than an excuse for a few friends to go out and shoot together. Well, we got "lucky"!
We've had two exhibitions hung, are in planning for a 3rd venue, (turned down a 4th) and have been featured on a regional TV show. We've decided we have to get "serious" if we're going to continue the project.
But, we all have other lives and none of us make our livings with photography. We travel and visit churches all over the (large) state when we can. So, we have to take conditions as we find them. It is a challenge that has become sort of a trademark of the images in the project that we make do with what we find. We can "plan" to visit a particular church, but we don't have any images planned. So, the artistic challenge, if you will, is to make something of the place once we get there. There is always some picture of some sort. Light may be flat, or contrasty. Many churches are very dark, and we rarely turn on lights because we find the artificial light to be less appealing (if more abundant).
So, I would have to say that luck plays a part in this project. Consequently, we often "fail", i.e., we come back with few, or zero usable images from a shoot. But, overall we're being successful, and most important, we're still trying to have fun.