Grafting Question

I am going to prune a Japanese Persimmon tree. One of my friends wants to try and graft a limb onto his Persimmon tree. When I cut the limb, how do I care for it until he gets it,in order to give it the best chance of succeeding.

Wrap it in moist newspaper, or paper towels, and seal it in a zip-lock plastic bag.

I heard you are supposed to graft fruit trees when they are dormant, is it possible to do it in spring or summer? I tried to graft something and i don't think it worked, so i'd like to try again this year. Any suggestions?

I'm not an expert but no I don't think so. I think that the scionwood -- not the grafting stock -- needs to be dormant. I don't think that actively growing stuff will take as well. With tropicals like avocados, cherimoyas, and mangos you want to take the scionwood just before it starts to "push" new growth -- or just as it starts to "push".