Well first off, I must say that I am a transgirl who has come out to both of my parents. 

But the point of this topic is to ask those of you who are more experienced whether or not I should test the waters so to speak with my best friend (who's a GG) and possible methods, or if I should just go ahead and blurt it out.

My main concern, obviously, is losing her, and anything you all could suggest would be greatly appreciated

~Tori

Just do it. If you lose her over this, she wasn't a true friend and there are more friends in the sea.

Testing the waters is really quite easy. Testing the waters about homosexuality is the same thing; generally peope who are gay-friendly are trans-friendly. If you live in California, bring up prop 8, ask what she thinks about gay marriage, etc. I guess that can work even if you don't live in Cali, it's just more relevant here I suppose. Another good idea is to research "holidays" regarding trans/gay issues, such as umm Matthew Shepard's deathday, or trans remembrance day, or PRIDE parades in SanFran or I've heard they have them in other states as well. Bring that up, see how they react.

If they react as gay/trans-friendly, it's all good. If they don't, I don't agree with Nero's approach to just blurt it out. Even if someone reacts negatively at first, they may get used to the idea over time and turn out to be really supportive. Just try a gentle discussion about whatever issue you used to test the waters, put out your own beliefs about gay/transgenders, if you're brave you can even try a "well if I told you I was transgender, would you hate me?" and go with that.

Best of luck.

How could you doubt her like that? Just tell her. She's your best friend, for heavens' sake. Trust. Trust betrayed reveals trust misplaced. Trust untested reveals trust that was never there. Besides, it'll be a lot less awkward for her if you can manage to keep a straight face when bringing it up. That will be a lot easier to pull off if you can have enough faith in her to realize she isn't going to blow some kind of gasket over it.

Remember: chutzpah can do amazing things. Helping you keep your friends is just one of them.

I'm not saying that you will have a similar experience but, all the girl friends that I have told have been very excited and happy for me. My best girl friend even gave me a high five....ok, I guess. LOL

Doesn't BFF mean that pretty much no matter what, they are your friend?  So tell them, if they blow you off, at least you will not be wasting any time on anyone who is not worth it.