Often times, I will get a girl's number, call her a day or so later, only to never hear from her. However, in recent months, I figured out a little trick that has worked 100% of the time.

Basically, I call a girl, and If a day and a half goes by and I haven't heard back, I will text her saying "If I was giving out grades on your call back skills, you would definitely get an F!"

I kid you not, 100% of the time, the girls have responded. Even if she isn't interested or whatever, the girl will text back with something. If she texts back with some excuse, I will then respond by saying "Terrible excuse, but at least you are trying. For that, I will raise your grade to an F+" This then usually gets into stuff about extra credit and how she can raise her grade.

EDIT: To help squash any doubts, here are some exact quotes from the last few time I have done this:

Me- Hey! If I was giving grades on your call back skills, you would definitely get an F!

Her- Haha that is fair. Hopefully that isn't the final grade!

Me- Well, your final grade depends on you. But I could probably think of some extra credit for ya, and raise your grade to an F+ hahaha

Her- Hmmm not even a full letter grade... What did you have in mind for this extra credit?

ANOTHER EXAMPLE

Me- If I had to give you a grade for your calling back abilities... I'm afraid I would give you an F!

Her- Haha i'm sorry my life is crazy! I was totally gonna text you today but you beat me to it!

Me- Haha yes of course. Typical excuse. It's ok, just embrace your inner slacker! Regardless, I will raise your grade to an F+

Her- Haha can I get any extra credit??

HERE IS ONE THAT DIDN'T WORK OUT

Me- If I was giving grades on your call back skills, you would definitely get an F!

Her- I just ended a 3 year relationship last month. It was/still is rough. Sorry dude... just need me time.

ANOTHER EXAMPLE

Me- If I was giving grades on your call back skills, you would definitely get an F!

Her- Haha sorry!!!! Things have been pretty crazy... I had 3 online exams and a glogster project due yesterday. I slept until 2pm today because of my lack of sleep all weekend.

Me- A glogster project? Tiffany, making up words won't save you. Though, for your creativity, I will raise your grade to an F+

Anyway, I highly recommend that you gentlemen try it out sometime. How well it works really blows my mind.

EDIT 2- I also just tried another variant with great success. I said "Bad news X, report cards are coming out, and I'm afraid you are getting a frowny face for your calling-back skills".

Her- Oh shit! I forgot! Hahaha! You would make a school joke [I work at a college]. I'm going out of town tomorrow and between work and pre-trip errands, I'm a total mess!

Me- Jess, Jess, Jess. Your excuses are bad and you should feel bad lol! But heck, let's say we raise your grad to a frowny face plus.

Her- Can I earn some extra credit!? Haha

Me- Yeah... probably. But if you slack on it, ooooh man, you will be in so much trouble!!

Her- I do kind of like to be in trouble though...

ANOTHER EXAMPLE

Her- Lol!! I'm sorry!! Work was crazy busy the last couple of days and I have been exhausted. I was definitely slacking a bit ;P

Me- Pshhh typical excuse lol! But for your efforts I will see if I can get your grade to a frowny face plus.

Her- Haha ok good... At least that's a start :)

Me- True true. There is basically nowhere to go but up. If you're free sometime later next week, let's go out and see if we can't raise that grade a bit.

Her- Ok sounds good to me :)