You can not bear that other girl is going out with your ex boyfriend anymore? All you want is get him back from her? Well, you knocked at the right door. I will direct you what to do and what not to get him back from her. I hope it helps.
First of all, you all will agree with me on this. We are girls; it's in our nature to be impatient. But whatever you are embarking on is not simple, so, a great deal of effort, hard work and patience is required on your part. And what have to be done, you will do it smartly and with grace.
You'll have to be prudent and cautious. Of course the other girl will not allow you to get with your guy easily. She may do mean things and if you reply back the same way, you may doom your work. You have to play it differently. This is to show your guy that the other girl is immature compared to you.
You have to be more mature and more original. Do not even think of fighting, disputing or whatever with the girl. Hold on your emotions, feelings, anger and frustrations. Remember, if you prove you are more positive and mature than her, automatically you become the superior alternative.
If luck is with you and the girl is not taking proper care of your guy then it is easier for you to win this battle. You may have a word with your guy's friends as they may share your opinion. If so, find ways through them to get your guy out of this bad situation. Get his friends on your side, that's the best way to get your ex from other girl.
If his friends are with you, consider the battle is half won. For that you have to show his friends that your guy is happier with you. When his friends will be against the relationship, your guy will sense it. This strain can crack the relationship.