Here is my opinion as a girl on this topic.... I think that if you are with a girl on a regular basis, there are easy ways to tell if she would even consider this. In all seriousness, if it is something that you are really interested in, then you should start with your hands and explore, and PAY ATTENTION to her reaction. That should tell you whether or not you should even get close to bringing up the subject of putting other parts of your anatomy there. I hope this helps in some tiny way.
