Eye contact flirting is all about casting your line out in to the sea of people and waiting to see who responds back with some bait.
This of course can be a lot easier in a room that is not very full, but once you have mastered your eye contact flirting you should be able to zone in on who you would like to invite further interaction with.
The method is really very simple. Scan a room and look to see who is scanning back. If you like the look of someone who is also scanning then lock eyes with them. If you can hold that gaze for three seconds of more, then the good news is that other party is definitely interested. If you you're female now is the time to test this person by looking down but not away. If they are still looking at when you return your gaze to there's then bingo! It's as easy as that.