If you broke up, there was a reason.
Forcing her or pressuring her to get back with you does not make her fall back in love with you.
If you make her jealous by being around a lot of other girls, she might come back out of possessiveness, but it won't last. If you remind her of all the good times in your relationship, she'll come back but then realise that those times are in the past. Etc etc...
It's only if you broke up for a stupid reason and both wish you could have just talked about it, or calmed down before making that decision, that you can get back together and still keep the relationship for more than a couple of weeks.
After my ex broke up with me, I cried for days and then somehow we got back together - for about 3 days. When it's over, it's over.