You've gotta get used to the disappointment, dude. No matter how much you flyer around town, your actual turnout to the show is always going to be a lot less than you expected for the effort you put in. For instance, for every 20 people you gave flyers to, only one showed up. BUT...That's 15 people who wouldn't have come out before and will most likely come and see you guys again the next time you play.
That's why they call it "building" a fan base. If it were as easy as passing out flyers and everyone who reiceved one would show up, every little band in the world would be famous. Unfortunately, it takes years to build a reputation and a good sized following.
One thing you should try is to head out to a venue you're playing exactly one week before you play there and hand out flyers to the people there. Chances are, if they're out on that particular night of the week...say a Friday...then they are most likely out and about every Friday night. And the fact that they are at the venue you are playing makes them more likely to come out and see you the next week.