One more piece of advice: don't talk with them for to long - even if things are going well. The longer you talk with them the more awkward things will get. I'd say there is a 3 min limit on talking with them. Just get their numbers and leave and set up another time to talk with them.
The only exception is if you are at an event (sports game/festival/amusment park) or in a bar/club.
xKei...x wrote...
.Ask her if its alright to introduce yourself or if its alright to ask for her name
No way, that is a bad idea. If you do that then the girls will think you are either weird or lack self confidence. Since you have already engaged in talking with them (since the moment you said your first word with them), you might as well say something funny or interesting. I'd say only ask for their names when things are either going well or right before you leave.
Example:
Group:[talk about ocean's names]
You: Well if you guys get any ideas let me know, but right now I (or we if you have a right) have to leave. We have to do [whatever] right now (you can invite them along if they seem interested.) Actually, if you have a phone number we can call you when we are done if you guys want to [meet up/get something to eat/ hang out] later.
[Get their number]
You: oh and btw I didn't catch your names... (if they didn't give them to you when you asked for their numbers.)