I've actually befriended someone I met through a SIFF movie last year. We both use 4square and he messaged me and asked if I was going to SIFF movies, and if that is how I was becoming Mayor to a couple of theaters. So we figured out what movie we were both going to see and ended up meeting and befriending each other from that.
I also befriend someone in line at a SIFF movie. I noticed he was at same movie prior and we talked about how awful it was. lol After that we have been going to movies together all year long. So get in line early to meet people! lol Go to the midnight movies. Higher percentage of intoxicated people looking to have fun...Higher percentage go to the English movies. Not many intoxicated people like to read subtitles.
There are inexpensive Saturday parties. They include a movie and small party. A little more intimate than the big galas.
Galas you have a huge amount of people you can meet. Wait it out during the parties, it is easier to meet people the later it gets. People have drank a little by then, usually people actually dance at Opening Gala by end of night, and the boring couples have left by then.
Volunteer for SIFF. I've met LOTS of people from volunteering for them. Work at the venues, you get to meet other volunteers AND talk to the people who are attending the movie.
Get on the SIFF Facebook and Twitter. Sometimes you can connect through people on there. And if you both like same thing or interested in same movie, it is easy to make a plan to meet someone at movie you are both interested in.
See lots of movies! Easiest way to break ice with another fellow movie goer. Someone asks someone what movies they've seen. What their favorite film of festival was. Then you can kind of find out if you are compatible with person if you agree. But if you haven't seen any, then you really have nothing to talk about... ;-)