Don't Be a Stalker
Avoid calling or texting your ex-girlfriend all the time. Give her a couple of days to cool off and then figure out a plan that she will like. Some women enjoy flowers and candy, some love certain foods and some love to be pampered. Give her a gift of something that she enjoys, such as having her favorite meal delivered, or emailing a gift certificate to a spa. Do this without having to meet with her her, as a face-to-face encounter may set up the potential for a bad scene. She may appreciate the gesture, but not be quite ready to talk to you or see you yet. Send a card with the gifts, asking her to call you or set a time to meet the next day. Meeting in the daytime or right after work will help take the pressure off of her that you are on a date, as an evening meeting may suggest.
Overly Sensitive Doesn't Work
Women want a man who can protect and provide for them. This doesn't mean that you have to be super macho, but crying every time you see her isn't going to work. Sensitivity is an asset in a relationship, but being wimpy and whiny about being lonely will push her away. Share your feelings about the relationship with her, but not about how terrible your world it without her. Talk about the reasons you split and how to fix those. Make compromises to get to the root of the issue. That is the kind of sensitivity that she will appreciate the most.
Confidence and Honesty
Even though your heart is broken, it is imperative to seem confident in yourself and your situation. Begging to be taken back rarely works with women, but you also don't want to be too aloof in your encounters with her. Acting like you don't care will also shut her down. Honesty is absolutely the best policy here. In the long run, if she doesn't care how you feel about the situation, then maybe she isn't for you. It's OK to say that you miss her and want her back, but refrain from whining and groveling. She wants to hear about how you are going to change what went wrong. This is the time to talk about how both of you can work on mending the problems.