There really is a small amount break up advice existing for men. There are lots of men just wing it when they decide to break up with their girlfriend. You could just take off on your girlfriend without any notice, but that would not be right. You should tell them what you are doing so you can let her down easy, do it the right way.
Hopefully the two of you have already talked about any problems there may be in your relationship and tried to work them out. If you prepared beforehand, your telling her you are breaking up may not be such a shock. You will need to meet her in person to tell her you are leaving, do not call her on the phone and give her the news.
Be sure you are at some location other than either of your homes; this puts the two of you in a neutral location Absolutely do not tell anyone else before hand because the chance of her finding out before you tell her are good.
When you give her the news, be honest about why you are leaving, especially if you think the two of you may remain friends. She may try to talk you out of leaving at your meeting or she may keep calling you later. If you have no interest ever in re-uniting, ignore the calls. Breaking up with someone is not an easy thing do, it can very emotional for both sides and you may feel bad about for days after.