"If I can't have everything, then just give me a taste."
That tends to work for me. Usually, the woman's penis is in my hand by that point.
Never text, always call, or, if you're daring, do it in person. Try not to sound too cocky or confident, otherwise you'll look like a tool or a player. You want her to feel special, and one way to accomplish that is to make it seem like you don't ask out many girls, but enough to know what you're doing.