One thing I have learned from friends who have made independent films is that you have to start promoting your film the minute it is complete... as a matter of fact, don't wait, as soon as you have a title run with it. This is your baby, your little brain-child so get out there and promote. Large studios have their own publicity departments but the little guy or gal has nothing but their reputation by word of mouth. In order to build that rep you have to work at it and there are various tools that you have available to you.
Previously there were only billboards or newspapers, and later on there was the television to get the word out there about your film. These were actually fairly costly and only the studios could truly afford these avenues. The rise of Internet has impacted marketing of independent film and the entire film industry as whole. There are so many different promotional tools that it offers you, it is hard to choose. The best thing to do is hit them all because you will need them.
When you are at the beginning stages of making your film start a blog. Once you have that going and you are making regular entries turn your attention to making a logo and then a website. The logo will carry though to many other things but for the moment it will help in making your website come together visually. There are services out there that will make a logo for you but, as in all things, it is always better if you do it yourself. The website can be made by you as well. There any number of sites out there that offer domains and website building tools.
Once you have built yourself a website then you can submit it to a search engine. Make T-shirts and hats with your film logo on them. A friend put her logo on panties and sold them. More girls bought those panties. These items made enough money to help her get through post-production. So, after you have made the regular website go to Myspace and build a Myspace page for your film. After the Myspace page is done, put something up on YouTube. These are all free for the most part so take advantage of them. Music artists have used Myspace to promote their music and it has worked really well so why not use it for the purposes of promoting film.
One of the more simple things you can do is to find someplace small that shows your type of film and will be willing to let you show your film. Make some eye-catching fliers and post them at the local college. There is usually an area for student public postings and fliers are all over these boards. College students love to see new and different material so if you can draw them in to view your film, that is a very effective way to build a following (dare I say cult film) especially if your film is quirky.
This about exhausts all the free or ultra cheap methods of promotion. Once you have your film to the point where you can do a premiere showing, you can consider preparing Media Kits to distribute to the local TV and radio stations. If you have gotten this big with your movie then you might even need a publicist. Now things are on a roll. Next stop, distribution