I wanted my next-door neighbour as an ally and resource person (she has contacts in the LGBT world), so I just came out and told her straight up. I just emailed her and said, "I know you work with LGBT youth. Well, I'm not a youth, and I'm not G or B. I am pretty sure I am T and therefore L."
For the rest of my neighbours, the ones I interact with the most go to a weekly kaffeeklatsch. So one week, I stood up at the coffee session and told them. I emphasized the gender dysphoria aspect, and that it was a medical diagnosis. Oh, and by the way, people with that diagnosis are called transgender. And that henceforth I would like to be called Kathy, and referred to with feminine pronouns. It was pretty painless, actually.