Just say 11.
That is a pretty tried number by myself and seems to yield a pretty positive reaction.
Do not say less than 5, they will think that you have been rejected a lot, or have had a girlfriend for a very long time and can't get over her.
Don't say over 30, or else it implies you count. You should start forgetting after 30, rule of thumb.
Do not say that you can't remember, even though you can't.
Do not hesitate. I suggest doing some role playing. For example, when the cute Starbucks girl ask you if you want "low fat," immediatly reply with, "11." Look her dead in the eye.
If you say 11, with no hesitation, she will never bring it up again. If you hesitate, it will be brought up on a once monthly basis, 4 times a month if you drink on the weekends.
