I can make friends and create relationships with just about any girl...My main problem is that a lot of the times I become just friends with them.

For instance, there's this one girl that I'd like to date in the future, but she has a boyfriend right now. I don't want to try and break them up or anything, but since I just started talking with her, and we're getting along fine, I don't want to send myself to the friend zone...How can I put myself in a situation where I'd be in a good position when she breaks up with her current boyfriend? What specific things?

Tell her you want to fuck her, and that she should call you if her and her boyfriend ever break up.

Demonstrate to her that your legit(a man, not just a nice guy) and if the times come, Bam you'll be filling that missing place in her life.

Also i wouldnt keep on her if shes already taken, just show her what you got to offer and step off and out.