Some pick-up artists recommend repeating something like this while you're out and about, both to give yourself thick skin and prevent the appearance of neediness: "Don't worry, they're just two-bit whores." I've tried thinking this to myself, but it rarely works. Maybe it's because the girls I approach are much too young for me to delude myself into thinking they're cheap whores. I probably wouldn't have much trouble believing that mantra if I pursued over-25 women, though, since by then they've probably been through their sluttiness bender at age 22.
Plus I just like being around girls -- there's something in my brain that won't let me view them like that.
But the pretty young things have their own defenses, chief among them cuteness. Their appearance and demeanor have been designed by natural selection to deceive you into thinking they're naive angels. Again, they aren't whoring themselves around yet, but their libidos point strongly in that direction. See this graph of total testosterone in females across the lifespan. Rather than go jump in bed with a series of strangers, they rely on fantasizing, touching themselves, and occasionally making out with their girl friends to relieve the pressure.
As with a baby's cuteness -- where the signal is honest, not deceitful -- a young girl's adorableness is meant to keep you from using or being mean to her. It probably also serves as way for her to test your sex drive -- are you going to shy away just because she looks too cute, or will you go for it?
Now, I remember all of my adolescence, and I remember all of the salacious things my high school tutorees have ever said, so on a rational level, I know they're not naive angels. Same for college girls. But on a gut level, their looks and behavior are still disarming. That's why you need something like the "they're just cheap whores" mantra, only suited to overcoming your hesitation in the face of super-girliness.
The key I've found is to imagine them saying something provocative enough to snap you out of their deception, but not so overboard that it's not believable. I mean, a nice white girl waiting outside of Hollister is never going to scream, "Get it daddy, that shit's yours!" But something alone these lines will help:
mmm, hold me tighter.
[giggle] ... touch it ...
Usually the PYTs roam in packs, even more so than older women. They're much more clique-oriented. This makes it even easier, because when you imagine one of them using the word "we," you'll snap right out of it:
c'mon, we wanna show you somethinggg...
do you like our bodies?
can we kiss you?
They all sound kind of cheesy, and not 100% authentic, but the important thing is that they're short, easy to remember, and effective. Girls vary, and some who appear innocent really are. But when they're somewhat young, looks can be very deceiving. So sure, you'll be disappointed by some false positives, but if you aren't armed with something like this to tell yourself, you'll suffer from even more false negatives -- "nah, she looks too sweet."