Are Your Answering Machine Messages Unique?
If you get the machine the first time you're calling the girl, make the message unique. Make it the most out-of-the-ordinary message that she's ever gotten.
Women love unique; they love creativity. If you want her to call you, you must grab her attention on that message. If you don't grab her attention and she doesn't call you, then you're screwed because the next time you see her, she'll avoid you because she'll feel bad for not returning your call.
The following worked really well for me. I had never had a conversation with this girl in my life, and ended up dating her for 2 months.
"Hi, this is Dave, Bob's brother. Why don't you give me a call sometime. In fact, give me a call tonight... at 10:04 PM. Talk to you then."
You can't make it sound rehearsed though. You have to give the impression that this is coming right off the top of your head.
Let's say she got home at 8:30. She spent the next hour and 34 minutes looking at the clock... trying to figure out what she was going to say when she called. That is exactly what we want. Now you have the upper hand... the ball is in your court. You've won her mind.
And an interesting twist...
When she finally calls, pick up the phone and just say "It's 10:03" and hang up. That'll get her laughing, and it will give you something to talk about when she calls back one minute later.
You're probably thinking this is either way too corny or way too weird. It doesn't matter, gentlemen. Women love corny... and they adore unique. Don't be afraid of either.