Focus groups are random, right place at the right time.

Early screenings are easier, you just have to put in the time. Extra tickets to them are provided to local papers and radio stations. In my city a major radio station "sold" them using points from listening. They'd give out one password an hour for the morning show, there was a site that recorded them, I'd go on the site every day, copy and paste the passcodes into the station website, collect the points, cash them in for movies I wanted to see.

My city isn't Las Angeles though. Their might be fewer available seats there than in my city.