Do a bit of research first – her likes, dislikes, analyze her pictures, recent status, mutual friends, etc. (which will be given in her profile page). The person feels more comfortable and interested to talk to when you have something in common to talk about.
Like mentioned earlier, how you start the conversation makes or breaks the chances you have with the person who you want to chat/flirt with. Start off with something subtle (like a compliment or enquiry) or something humorous as everybody loves humor!
Initially, let the conversation take its path with an upbeat tone. Do not open up yourself completely within the first few chatting sessions, like telling embarrassing long stories of yours or anything else for that matter. This can turn out to be a real turn off. So, make it simple, funny and interesting!
Whatever you do, do not reply to the IM as soon as the person replies as that can be analyzed as desperate or creepy to the other person. Also, do not constantly ping the other person and piss her off and do not send long creepy voluminous messages.
Once you figure that the person is interested, bring in your real game! Start off with mild flirting. It is said that a lot of men and women love a witty use of sarcasm, but that doesn’t mean you play that card 24×7.
The final thing to seal the deal is to get her number. I mean, that’s what you need at the end of the day right? Right after you think that the conversation is interesting and have made her laugh, you tell her that you have to go right now and that she/he can continue the conversation over the phone and then give her your number and log off. Sooner or later, she will try contacting you, provided that you have succeeded in making the person interested in you.
So, there you go! The tips given allow will give you the confidence to flirt/chat with a girl online and at the end of it, get her phone number.