May I jump right in and see if I can coax some other girls out? As I've been out at all hours and have done it for years, perhaps this can be of service: (mods feel free to edit this away, since I'm not sure where this type of info belongs)
Go out in the morning (if you can), your shave is closest then, and less people are out in the morning than at any other time of day. This will also help you if you choose to dress conservatively, since no one expects anyone who's not working to be all dolled up before 10 A.M. Blending is the goal overall, just look appropriate for the time you're out.
Head up, shoulders back, big smile, aaaaaaand walk (Haha). Seriously, confidence is killer. Even if you don't pass, but you maintain your cool, people are less of a threat to engage you. Also: Practice walking in heels before you go, if you stumble it's a dead giveaway. You know what? You don't even have to wear heels, the way that gravity forces your toes together can be a pain sometimes.
If engaged (questioned, whatever) be cool. Try to be charming and polite. Odds are that the person you're talking to will never talk to a trans person again - it takes courage on their part to talk to us. Best to give a good impression. If someone clocks you late into an interaction and they freak out a little, just smile and conclude your business (happens to me all the time).
Your hair shadow and your excess tracheal cartilage is not always going to give you away, it will actually be your voice that does it. If you must speak, do it quietly, unless you have a working female voice.
*** At some point, after stepping out for a while, I started to evolve socially. I WANT to talk to people, I need people to approach me and be friendly. I can't help it, I'm just bubbly. I'm sometimes grilled by my S.O. for being too cutesy, and generally the type of girl that I assume other girls hate to be around because I make them sick with all my sunshine. I say to heck with all that. Go out and have fun. Sit around in dept. stores and make them boys bring you 10 pairs of shoes, take dresses into the fitting rooms, flaunt what you do or don't have and leave them gawking. Life is short, live it.
Well, now I want to go out and got no friend to do it with!