Since I don't describe the things I do as spellwork, magick, or magic, then I'm not sure I would call my method of imbuing stones with energy "charming" them.
However, you might want to look up information about programming crystals/stones. Here's one link that give some information about it:
http://crystal-cure.com/article-prog...gemstones.html
Note that unlike the last part of that site's writeup, I have never had stones "corrupt" or "exchange" programming by coming into contact with one another. So I wouldn't personally worry about that part.
Uma Silbey, whose crystal handbook was the first one I read (and is still my favorite), described her practice of using breath to carry intention. She advises forming the intention clearly, and then "blowing" it into the stone until you sense that the programming has been accomplished.
Some people who work with stones can sense the spirit of the stone itself. But those are intrinsic to the stone, rather than being something that a person has put in the stone.