Just be honest and up front. Don't gush over her telling her how great she looks, etc. Tell her you would like to photograph her and tell her if she likes, she can bring a friend (male or female) or relative. Some times you get lucky and the 'friend' is worth shooting too. Offer to meet her on her terms - that is at a location she is comfortable with. It also helps to have cards with your number on them. Be prepared to pay the going rate, unless you can work out something with photos instead of cash. It's been a LONG time since I shot any models in the Detroit area, but going rate was around $50 per hour, probably double that now.
And don't drool...