How best to turn them away?

Tell her she is too old for you. If that’s not enough, just confide that

It might be an indicator of the dates I go on that this comes up with unfortunate frequency.

But if he can come up with one, he deserves a gold star!

How about, “I’m trying to catch a disease. Have you had any interesting sores or rashes lately?”

Well, here in LA if you say you have a screenplay in production and would like some input from her she will run, as she is sure you are going to try to steal ideas from the screenplay she has in production.

Or, “This new relationship with you will save me a fortune in hookers.”

Or, “I assume you are into pain, are you not?”

Or, “Let’s skip the dinner out. I think my Viagra is starting to kick in.”

“What do I like about you? Well… the pastor said I’ve got to give going straight a shot or I’m going to burn in hell. If I squint, with your figure you kind of look like a guy…”

Inviting a girl (one you don’t know to share your hobbies) to a trekkie convention or to watch your live role playing thingie seemed to work real well for some guys I knew in college too. Sadly, they weren’t trying to drive girls away.

Win a $2 bet to eat a trout’s eyeball raw. It worked for me when I was a camp counseler…except that then then tomboy girl thought I was the coolest thing EVAH! But the tomboy girl didn’t force her way next to me on the bus and rub my leg, so that wasn’t a real problem.

You’re good, but there’s this thing your mom does with her tongue…

“…I play Magic: The Gathering…”

“I’m a grad student.” works well, too.
(past that, fortunately, but still speaking from experience!)

during a night out to dinner ask if she thinks the watress would give you a bj in the bathroom while gf has some hair pie lying on the floor soaked with pee tell her its a huge turn on and has allways been a fantisy to do something like that

If you have good health insurance:

“You have small tits for such a fat girl.”

Or possibly good life insurance.