How long do you hold eye contact and keep silence before breaking it or before it becomes creepy?

I've tried to figure this out so many times! When I'm sober and talking with girls (or drinking), I don't get the strong responses to negs and jokes as I do after a bowl or two.

Example:

Saw this chick I knew on campus last year with a hot friend. I tried joking around with them but only the chick I knew was receptive. Then me and my friends smoked up with them. I don't remember what I said to the hot friend, but I threw a neg, no smile, no movement and just looked her in the eye and waited (didn't do this intentionally. It was due to the weed). She looked at me, smiled and said "shut up" and I could tell it was on.

Next example:

Smoked a joint with a friend and went to a restaurant for some beers with my other friends. My friends aren't the smoothest bunch so they weren't too suave when the HB9 waitress came by. I was composed, talked with her, maintained eye contact and everything just felt comfortable. I could tell my eye contact was turning her on.

So when you're talking with a chick, how do you maintain eye contact without looking creepy? Do you wait for her to respond and stare at her until she does? Why does eye contact and silence only work for me when I'm blazed?!

Any info on this topic is much appreciated! I feel like my talk-game is good, body language getting better but if I could get this eye contact and silence thing down, I feel like I could step my game up tenfolds.