I've been reading posts about losing friends and people getting freaked out when people come out as trans*. The argument of "I'm still there same person", " it's still me inside " etc seems to fall on deaf ears. Even for me, I am different as I transition. But here's my point, the change is soooo slow (could be many months, or even years) people don't notice. Let those friends transition with you. Don't tell them. Let them learn about the new you as you do. Eventually they will either stop calling or be unavailable but then they are making that decision on the new you not "trans* you."
I see three exceptions
1) obviously medical professionals
2) your immediate family
3) those people you need help from during transition.
#3 is the "other" bucket, but the key is, you must tell them. For example hair dresser/stylist. Maybe (and this is a huge maybe) H.R or your manager.
I'm thinking a slow, let them get used to my mannerisms. Typically people are so totally oblivious to subtle changes they might not even notice at all until you wear a dress one day.
Things that might get noticed:
Hair length. Mine is longer now than in the last 30+ years. The comments have been "wow, retro 70's". To "wow, I love it.". No one has been negative.
Ear piercing: yes this is a big one. Maybe really small studs? I'll take suggestions on this one.
Breast growth: by the time they can't be hidden, I would say they are either with you or not.
Then the rest, name change, FFS, voice, etc. But by that point, you might have a better idea of allies and non-allies.
I would love other's opinions on this.