That's always an interesting concept when you try to make your dream into a reality and you come up against the facts of exactly what it is you're attempting to do.
If I read a script and find it engaging and I start making choices in my mind on how to approach the work, than that's a good indication that it is something worth pursuing.
There's only so much you can do until you get on set and see the aesthetics of what you're dealing with. Then you see what the other players are giving to you. It's all about the transfer of energy between different actors.