How do i ask this girl to be my GF...I know shes gonna say yes...but how do i go about it ?!?!?!?!?

Im a freshman in HS and I know this girl that has apparently liked me since last NOV. She talks to me a WHOLE lot online but in person she seems kinda nervous or uncomfortable around me. She don't talk as much in person as she does online. I really dig her... im the school mascot and shes a cheerleader soooo...we spend alot of time together. I want to know what would be the the most comfortable way for me to ask her? i don't wanna make her uncomfortable around her friends...and i don't wanna make a BIG scene!!!! Im a funny guy so If you have answer that contains humor that would be good...thanks everybody!!!