Ay, that's the rub.
The best way to finance a film, that I've figured out, is to find somebody that may have an interest in your film, more than just liking going to the movies. For example, one of my films I did at the beginning of the summer was about how a man deals with his own mortality. I remembered that one of my friends' fathers owns and runs his own mortuary, so I went and spoke with him. Not only did it share his interests, but he liked that thought of making a movie (I guess it's just one of those things that's so dang sexy!).
Other ways, and I'm doing this right now, are find out who owe favors to your best friends. I have a friend who has very rich friends that owe him some big favors. So, not only is he producing the film with me, he's also getting the money to do it for us by calling in his chips.
Lastly, of course, is the plastic option. More than one successful film has been made on credit cards. The only caveat, however, is that you better be sure you can do something with it afterwards, because you don't want to be stuck with thousands of dollars in credit card debt.
Of course, you could also rob a bank. Be creative!
-T