1) start to know the boss over there a little bit, his background (if he is from the same school as you, etc, wife go to the same church, etc, j/k).
2) get to know him - through networking, meeting, etc. If you have no such opportunity, write him an email and ask him information about HIS group and want to know more about them (inquiry). Don't talk about yourself at this moment. You can thank him for sending you information, pay compliments, and say that his group has a wonderful future in the market and wonderful future in the company, etc. If he asks about you, then the opportunity is coming, and you can stand to present yourself as a great helper to him to achieve those wonderful things.
3) let your current boss know as soon as possible when you feel that you have something good going along other side. You don't say you will transfer, but rather say you are very interested in other project, etc. He will understand immediately.
4) there are lots of details needed to be carefully crafted. You better think through hard before any action. It will all depend on you to achieve the goal of transfer.
5) always do your work as best as you can in the current position.
My 2 cents. good luck!