Cool guy's are every hard to attract because they already have a gaggle of women around them.
But, that isn't always a bad thing. Sure it means there's more competition for him, but that's what dating is all about right? Competing for the best match, the best mate, the best guy.
So, if you're sure he's the guy for you, he's past your tests from a distance, which means:
You've been able to observe him and how he treats the women that hang around him now and he's not a total jerk.
You've looked into his dating history and he's not the "love 'em and leave 'em" type of guy that will break your heart.
You know that he will be committed to you when you do start dating him.
If he's good on these three things then it's time to woo him.
Get his attention.
Make him love you.
Investigate him. Make sure that he isn't a total jerk towards women, that he will show you some respect.
Study your competition. Your first reaction might just to dismiss the other girls as tramps (or worse) but they are surrounding the cool guy for a reason, watch the how's and the why's of what they do.
Find out some common ground with the cool guy. You're not a door-to-door salesman, this isn't a cold-call. You know how your target is, so you also need to know some stuff about him, what does he do that you also do? Do you have common ground to start a relationship? Once you have that information then you need to plan your approach.
You need to get his attention so the first thing is to wait for him to be alone, or with a girl of less status than you. Walk directly towards him and say something like "Hi"... but just not so lame. Remember, he's a "cool guy" and he is used to a certain type of treatment from women.
So, the first thing you say is "Hey, you were really good at (whatever last sport he played that you saw him)..." a little bit of praise always opens the door for some more detailed conversation. Keep the conversation going for about two minutes, not much longer. To escape the conversation you say "I gotta run, call me (and write your number or email address on the palm of his hand) and walk away.
Your knees are shaking, you're sweating, you feel sick. But you now have the cool guy's attention, so now just be patient and wait for his call or email.
You've done well. Good luck!