Jballou- I finally feel like there is question on here I can really contribute to. I’m a filmmaker, a friend of this site (the shadowy figures behind it), and a flutherer, so if you have any specific questions feel free to send them my way.
There are a million ways to answer your question obviously because there is no set way for this to come about. Yeah, I do think approaching private investors directly is a good idea, depending on the scale of the project. One thing, if you haven’t done it, is to make a short. I think someone mentioned that- but it is pretty important. I would say make a short for whatever money you can do it for and convince people (even in your own network) that you are credible and capable of making a film. Having something to show, even versus having a perfect script, will help you raise money. Then I would suggest reaching out into your own network first and seeing what kind of money you can come up with. Depending on the size of the project, one good thing would be to have an experienced assistant director break down the script and estimate the costs. If you know a good DP start talking to them about format, etc- if you can achieve the result you want based on how much you think you can raise. Figure out how much you think that you need to do your script and to do it justice.
To sort of answer the bonus question- there is not a set way actors get attached but if you know any casting directors sometimes (and this is mostly what I’ve heard) those people will bring in your name actors. For instance, I believe the casting director of Half Nelson brought in Ryan Gosling. That was on the commentary if I remember correctly. If you have actors that are perfect for your script, you can try sending them or their agents a polite letter. Certainly if you know a name actor you should write a character for them and get them on board but if you don’t (like most people) just go ahead and raise the money without anyone attached. It will be harder but most people are in that situation.
One thing to consider, once you’ve made your film, you have to think about distribution. Unless you have a distribution deal in place, in which case, we wouldn’t be talking about this. It may not be for you but look into getting a producer’s rep or sales agent to sell your film.
I realize I’m sounding kind of all over the place but if you message me and I’d be glad to address anything specific I can.