Someday, when I get around to it.
Which usually means when it’s on tv or I can borrow the DVD.
Back when I lived in a city with a movie theatre I would go watch a movie more often, but right now I would spend more time and money getting to and back from the theatre than I would spend actually watching the movie. 
Mostly on Netflix, which was sadly left out of the poll as an option.
There are only two or three new films a year I’m very interested in, and then I’m very interested in them I wouldn’t like to spoil the experience by watching it with dozens of people who obviously aren’t, so I wait for the DVD and watch it at home with my wife.
I thought Netflix’s main business was still renting DVD’s so “when it gets released on DVD” would be your option. I know they also show movies via computers but I thought this was subsidiary to their DVD business.
Netflix on-demand streaming is overtaking their optical disc rentals.
I picked “someday, when I get around to it”, but that’s not really a very good match. It depends considerably on a variety of circumstances. I usually won’t see it opening weekend, unless a group of friends wants to go then. If it’s a movie I really anticipate I’ll like, it might be about a week after opening (though probably not on a weekend), long enough for reviews to come in. Sometimes in the summer when it’s really hot out, I’ll just pick whatever current movie appeals to me most, just to stay in the AC for a few hours. Sometimes I’ll deliberately wait until a flick hits the on-campus second-run, and sometimes I’ll notice something playing there and decide then. If I don’t get around to it before then, or only hear about a movie after it’s out of theaters, sometimes I’ll see it on DVD.