CHOKE kink

Had never choked anyone in my life, my girlfriend told me she liked to be choked. We dated 25 yrs ago, life happened, both single and started dating again, we start talking about what we like or would do or try and she told me she's not opposed to being spanked some and being choked. I can pop her ass, I'm no prude and can be playful and stuff, I've just gotten to where I can put my hand..hands around her neck, I'm not choking her out, just a firm grip, she says it's ok, she likes it, I'm still just a little apprehensive about the whole thing. I mean I wanna do it because she says she likes it but don't want to go to far and she's like..WTF are you trying to kill me. That being said, I do it for it, I'm still feeling kinda uncomfortable about it, but it's hot as fuck when I do it, and her sounds change, she fucks harder, I seriously feel her pussy get wetter.

ANY ADVICE on how to go a little farther?