You really can't beat honesty. And if you're somewhere where you feel like you can't be honest, then you really need to question why you are there in the first place. Having said that, though, I certainly wouldn't advertise the fact. In my case, the less noticeable it would become during transition, the less questions would be asked me, and the less I would need to divulge over time. So, minimizing the questions would be my goal - not coming up with lies or excuses. Those in my inner circle, like a lover or anyone that I'd hang out with one on one, would certainly know my past. If I didn't think that they would accept me for me, then I wouldn't waste my time or energy on them.