I think a bunch about promoting my films, and I seem to be relatively successful since i have a decent number of views.
The most important thing, of course, is to make good content so when people see it they'll want to watch more.
Once you've done that, there are several topics on BiM which allow you to promote your film in a non-intrusive way because it's kinda the whole point of those topics. The frame from your upcoming film topic is a wonderful film, as when you post a frame you can show something which might give people some interest in your new film, you can also put in a few words and tell people more about your film so that they might want to see it when it comes out.
There is also a topic for posting movie posters, so you can make a poster and put it there. I took some time to make a poster for Leprechauns in France to post there, on my twitter, and FB page so that a bunch of people could see it.
If you are making a much bigger long taking project, you might also make a production topic as an update log for your film. I've been doing this for my long Batman film I've been making for a few years now, and I've gotten some useful feedback, as well as spread some word about the film to people.
Those such topics don't seem very appropriate for very short films, though.
An important thing to do, though, is not spoil your film. Don't post spoiler frames or give out spoiler information. You want the jokes to be fun and fresh before everyone sees it. Some people will occasionally make one joke films but spoil the joke in a small bit of promotional material, which kinda ruins it.
I'm very tempted to spoil things about my films, but I try not to because I want it fresh. Unfortunately most of my films involve really weird random humour throughout so I can barely tell people anything about my films. For instance almost nobody really knows what's going to happen in my next film.
It's also important to make your film look good, but not too good. If you oversell it people may be disappointed by the final product.