see Ansem I'm going to try and explain how most guys will react if caught drooling incoherently by the hot girl in question but it's going to be hard for I react differently to the normal (as to what I've seen of my mates who hardly believe my audacity):

[guy1] "omfg look at that she is soo hot."
[guy2] "sure is oh feth dude we're rumbled umm look away now!"

right I know that is pathetic conversation but its hard to explain. my reaction when rumbled is generally:

[me] "now that my friends is some seriously good looking girl over there" (follow this with a comment based around the clock where straight ahead is twelve to point out who I mean)
[my mate] "hahaha dude she soo over heard you look she's looking over now, dude your on your own" *walks off fairly embarrassed*

[Girl] "what you looking at?" (you know the score not all girls are able to appreciate a man looking at her derriere)

[me] "...just a hot girl, who i don't yet know the name of."

after that I either get talking to the girl in question or she walks of but bear in mind I have never once been slapped by a girl for this and they generally appreciate my boldness to remain calm and immediately trying to get to know them.