Please help me, first time asking a girl out in this situation

Hi Guys
My situation is that there is a girl i like, we talked outside university once, I tried to ask her out the next time i saw her (next lecture), on monday, but she was surrounded by 4 friends, so i had no chance to ask then. She is not in my tutor group which makes this even harder if every monday she will be with her friends. Today, after class, i waited for her to leave the classroom by herself but a guy (who 2 weeks ago told me he had a girlfriend, and i saw them) was talking a lot with her and was waiting for her after class; they both went out toghether, so my chance was ruined by this guy! I don't know if she likes him now or knows whether he has a girlfriend or not
(he could have broken up with his girlfirend but this particular guy is usually alone in class, doesn't talk to anyone, don't know if this helps you help me out). My question is, how or when should i ask her out. I don't know how to ask girls out, if i had saw her today i would have asked her if she would let me copy her notes because i didn't get much written down, and then tell her to wait for me at break time next time we have a lecture to walk around the city and talk. Is this how it should be done. Please give me your opinions and try to answer the various questions i have posted, i would be very grateful. Thank you.

This is what i think you should do

I think you should: easy part find any excuse to hang out wit her , if she is with friends tell her can i talk to you alone and walk....... once with her
you should come out smoothly , try not to get nervous be confident value who you are and tell her that you like her company a lot and in the few time that you know her that you realized you enjoy her company and ask her if she would like to join you for a dinner or a cup of coffee or find out what she likes or where she loves to go out and go there.........usually by doing this it pretty much means you like her and you want to get to know her, if you think she might not get it , tell her that: I would like to get to know you better...... she should have it clear with that and take it from there.... be yourself with her do funny stuff to make her laugh and compliment her n stuff but be yourself......Godd Luck

Now!!!

Oh my loveliest, darlingest boy. Go to her on monday and even if she is standing up at the front of the classroom just ask her causually if she'd like to come for a drink or to watch a movie or best of all to do a bit of pair-study in the uni-library. Doesn't matter what you say really cos if she's nice and right for you she'll be thrilled by your invitation of friendship. But don't come on too strong she wont want to be accepting your marriage proposal. Start as friends and work from there, before you know it you'll be snogging at graduation! Good luck my darling! XXX