I LOVE choking girls, it is so hot and they get so submissive and just EAT it up. The best way to do it is to grip her neck at each of the jugular veins on each side.
Don't grip hard, light is fine and some girls can handle/prefer a moderate grip. Just enough to deprive her brain a bit.
You don't want to put pressure on the windpipe, just light to moderate pressure at each jugular. When doing a missionary variant where you are supporting your weight above her, what you do is put that pressure on her collarbone right underneath her neck. This will still make her sore, especially if you are pounding her and weigh a lot more than her, but it's doable and lets you choke her without crushing her windpipe.
Another awesome thing girls love is choking with one hand while sticking your thumb or fingers in her mouth as you grip her face with your other hand. One of my favorite positions is pinning her down with her legs over my shoulders, pounding deep into her as I choke her, and making her suck my fingers and/or thumb. SO fucking hot, I get hard just thinking about it
Try it out and hopefully you can blow some girls' minds.