the best way is to ask her in identical threads posted twice daily until she gets tired of it and submits.
"Hi, I think you're pretty, will you suck my cock?" It might not work most of the time, but it sure gets right to the point!
when you say "pretty woman" are you referring to julia roberts? have you seen the size of her mouth? talk about a hotdog down a hallway.
I usually start out by talking about how women love to blow me because I have such a small penis. I then let her know how women love feeling like a pornstar cuz they are able to take me all the way without gagging. Works every time.
Start by asking if she wants to take a nap and offer her to rest her head in your lap, while watching tv. And then once she gets comfortable, take deep breath and then calmly say "it ain't gonna suck itself" Muahhahaaa! (Count Dracula laugh)