Phew, there is no thing set in stone when it comes to this. Parties are living environments and unique. There are many things to consider at a party, interruptions which ****s up your enchantment on her, AMOGs, her friends and similar.
One thing which have worked ok for me in the past was to talk to the girlfriend of the girl I was interested in but a girl who also had a boyfriend so she could talk like a buddy to me. Then I would move on to my target. Why did I do this? Well girls friends got a ****ing annoying ability to interrupt when stuff are getting hot, if you get some rapport with her friends they wont mess up for you as much. Even had a girl who enjoyed talking to me so she brought me one of her single friends and pretty much pushed her at me.
What you should avoid is to LEAVE the girl after you have made contact with her. If you leave her then you will have to start from scratch again and some ****head guy might show up and screw up your game while you are away. People feel some sick need of mingling at a party, it is not needed if you are gaming a girl, IMO it is counter productive.
Talk to her -> get rapport with her -> isolate -> profit
Dont ask on a date if you can avoid it. Only do that if you cant get her to sleep with you or if you are not meeting her regularly. If you meet her often then talk to her and do a instadate instead. Taking numbers and setting up dates gives a wierd environment and women tend to flake if interest is not high enough. Just grabbing a cup of coffee after you bump into her gives a much better atmosphere.
Your buddy is right about isolating though. Do that as soon as you have enough rapport with her to avoid **** blocking friends/drunks and stuff that ****s up your game.
Edit: No point in smsing her before you get there, just dont lunge straight for her the minute you step into the door. Mingle a bit before THEN talk to her and dont leave her.