Like with everything else, if you don’t know how to do it yourself, in your case casting brilliant actors on the cheap, go to someone who does. You can ask a filmmaker who’s gotten good actors in their project or, better yet, approach a professional casting director who’s cast low budget movies you’ve seen with remarkable talent. If they respond well to you and your project they might work for next to nothing, especially if you throw in a producing credit. These people know the special waters you’ll be in and, beyond setting you up with a solid cast, they might even bring you an extremely special find, some genius actor who hasn’t hit it big yet for the reasons I mentioned earlier.
Do not use the assistant to a major casting director thinking you’ll be getting this person’s insider knowledge. This happened to me when our producer hired a Prada wearing minion of a big deal casting director, who I’m sure was very good at taking lunches and politicking with people from big agencies, but before we fired him when he made himself unavailable (due to his vacation plans in Palm Springs) he’d wasted a week of our time going over the same lists of talent everybody else goes over and talking about buzz. Buzz shmuzz. You don’t need conversation for a cocktail party, you need an actor who’ll take the hill when you say: “Action.”
If you’re not in L.A. or New York, or if you’re going to go non-union (and maybe even if you are and you’re not), then go to the folks in your area who know the good local actors and ask them who you should use. This would be the local theater companies, college drama departments, film schools and acting schools. Maybe your local paper’s theater critic has seen someone amazing. See if you can sit in at a theater group and watch a few people. Come on, that would do you some good, anyway. Maybe you could add incentive for an acting teacher or a director by making them part of the project, tell them you’d like them to come to the first reading of the script and give notes. We’re suckers for stuff like that, feeling important and participating in a real project… wow.
Also, of course, you should watch tape. A good actor is a good actor and it’s much better to see somebody doing their thing for real than to judge from an audition only. As to that, here’s my advice on actors coming in to read for you. It’s crap. Is it your idea you’re going to have an artist come in to a little room with knickknacks and sit in a chair in front of a sofa and a plant and read some pages opposite someone who either isn’t an actor, or is an actor with nothing at stake, while you chose whether to validate them or not, and that this is going to tell you the person who’ll bring your movie to life? Research shows that when African Americans or women are told they’re being tested in order to make a societal comparison of race or gender they test lower than white men, yet when told it’s just for general research purposes they then test the same. White men demonstrate less vertical jumping ability when tested by an African American than when tested by another white man because, well, you know what they say about white men. It’s called choking, my friend, and there’s not an actor worthy of the name that doesn’t come to into that room without a highly charged sensitivity for how their offering is received; and some of the greatest actors, guys who will be blazing on a set where it seems like something artistic might be taking place, tank when they feel the pressure of a thumbs up or a thumbs down on their worthiness. If you have to choose between an actor who gives you a good reading or one you feel is right for the part and you believe to be the superior actor… even if they stink up the room, paper trembling in hand, zero pizzazz; go with the good actor.
