How do look up girls skirts?

Because they are perverts.

Either you will get caught or the girl's skirt you're looking up is not the smartest in the world. But she'll be wearing underwear 99.9% of the time anyway so what is the point?

Yes. Many places it is a crime. But where ever you are, people will think you are creepy. If the girls haven't told you that its OK, then yes it is bad.

Of course.

When they sit down, slide underneath them without them knowing (;