Women, typically, can read our minds. Which, believe it or not, gives us something of an advantage. If it's a woman you might be interested in, imagine yourself having sex with her when you make eye contact. You have to be smooth about it, don't pop a hard on or anything, but imagine yourself on top of her, staring deeply into her eyes. Women know what we are thinking at any given time. The great thing about it is women are trained, subconsciously by culture and society, to be suBathmateissive to men. If she's open to something more than being friendly and she continues to hold eye contact, you'll notice sparks flying. You're already giving off sexual vibes and the odds are that she's already thinking about you sexually. If she's just being friendly, you'll notice that, too, and you found out what her intentions might be before you even made a single investment with her.
Lust is a tool that you have to use sparingly. In any seduction, you should stay at 90% calm and 10% lust. Don't let your lust go unchecked, at any point, until she's ready to cum.
If you can control the state that you are in it will make it 250% easier to control the state that she's in.
If she's a slut the extended eye contact should pretty much close the deal for you.
Enjoy!