In the last year and a half I've come out to everyone in my life, and I've had really good reactions and acceptance towards it.
One of the main things that I think helped was coming out to each person individually, in a way that I thought was best for that specific person. Everyone in your life is different, and each person/group will respond better to different methods, wording, and scenarios. And there are a lot of different ways of doing this. :]
Here's some of my experiences:
The first person I came out to was a university friend who I had dated for about 9 months while we lived in a shared house. After uni I moved back home, but we kept in touch online mostly. He's a very kind person, and if anyone was going to take it well I figured it'd be him. But he was also my first choice because telling someone over MSN (that I didn't see very often any more) seemed like a good test run! If he didn't like it, it wouldn't really impact on my life.
I'm very glad I did it over MSN because coming out for the first time ever was really emotional, and I wouldn't have been able to speak for the tears.. Luckily I could still type. :p
Fortunately he took it perfectly and has been really sensitive and accepting. He also came out for me to his group of friends from school who I've met a few times, but are usually around when we do meet up, and that group (who I rarely see and aren't very close to) took it fine as well, and were the first to make attempts at using correct pronouns.

To the majority of my friends, I came out kind of spontaneously, after I ended up alone with one of them and it seemed like a good time. Often it was after a few drinks, which seemed to loosen my tongue and soften the blow a bit. All of my different types of friends have been very accepting and awesome, so I guess it worked.
The ones that were a bit more shaken up by it were those that (I usually found out afterwards..) had a crush on the "female" me. Understandably, it took them longer to adjust, and if you can't figure out why someone who's quite close to you is acting a bit odd in response, this could be a possibility.
Coming out to my family was interesting.
I found it quite difficult with my dad, although he was accepting. He has always been very "I want the best life for my child possible", and I think he had a hard time swallowing the fact that transitioning could potentially be detrimental to my career and relationships and such. He didn't really understand that not transitioning would be detrimental to me personally. He jokes around a lot, so it's hard to tell what he's honestly feeling (And I'm the same way.. So having a serious conversation between us is tough.) But I know that he doesn't love me any less and that he's been trying to support me any way he can.
He came out for me to my grandma (his mum, who hadn't seen me in 6 years and doesn't speak great English) just before I started T. He must have done a good job though, she seemed very accepting straight away. She's visiting us at the moment and she's always calling me her "boy", using all kinds of male pronouns and generally being very cool.

With my brother I was pretty worried about how he'd take it, but I just came out to him during a casual chat in the park, and he said he had actually been suspecting something like this anyways. He seemed totally un-phased (though he rarely is) and he refers to me as his brother now. Though I damn his full beard at 17 years old, he makes me look so much younger next to him! P:
My mum has been totally on board with everything from the moment I came out to her. I invited her to a quiet corner in a pub one afternoon and just told her straight. She's the "I want my child to do whatever makes them happy" kind of parent, so it was a lot easier. She first asked me if I might be a lesbian when I was 16, and she didn't quite believe me when I said no then, so she said she had been expecting me to come out as gay when I came to talk to her.
My mum also came out to her [big] side of the family (who live up North and hadn't seen me in about 6 years on average) for me, and I hadn't really appreciated how well they'd taken it until we went up there for my cousin's wedding a couple of weeks ago. Everyone was great, I was seen as male, even by my 4 and 6 year old cousins that had seen me once before (a little over a year ago) with long hair and in a skirt for my mum's wedding. Now they believed I was bio-male, and they were really attached to me.

My grandpa who hadn't seen me in the longest time (10 years) seemed totally comfortable with me and had totally switched pronouns. I was really apprehensive about the trip just because of this, and it turned out really well!
At work I talked with an HR woman for quite a while before coming out.
I came out directly to people that I worked closely with, mostly telling them while outside of work, but I never got an opportunity with my line manager and the two girls I sat next to. I just said to them "Can I have a quick chat with you upstairs?". I spoke to my line manager on his own, and the two girls together. They were all very cool with it, and actually the time with the two girls was the only time I've personally come out to more than one person at a time. But it worked well - They kind of bounced questions off each other, and they each had some time to think while the other (or I) was speaking.
Anyway to the rest of my colleagues, I wrote an e-mail that the HR woman sent out to everybody for me while I took the morning off. My reason for doing it by e-mail was that I can't stand up and talk infront of a room of people about a Lot less stressful topics, never mind coming out to everyone as trans. If you've heard about a lot of people doing presentations/meetings at work, you don't have to do it like that if you don't want to. I got it sent out it while out of the office because I wanted to give everyone a chance to read my message (and for me to know that they've read it - some people take a few hours to get through all their mail), soak it in and decide how they felt about it before I was having to talking to them about work stuff. I got no negative reactions from anybody at work (80 people working quite closely on one floor), and had quite a few positive replies to my e-mail.
However, very rarely did anyone remember to use male pronouns for quite a while. In fact, it wasn't really until after I was gone for a month.. Then people had magically switched when I came back!
The day after I came out at work, I came out to.. Facebook, which included pretty much everyone else in my life that I hadn't/wouldn't get a chance to speak to in person for a while. I wanted to do everyone before starting T. I made three different categories of friends and sent three variations of messages out, depending on how well I knew people. I got tons of responses, all supportive. I even sent a short message to old school friends that I hadn't spoken to in years, since I was changing my gender on my profile and wanted them to know from me, not from somebody else, why that was. It was nice to re-connect with them too.

And.. That was me done. Everyone that I care even a little bit about now knows, and I feel really honoured that nobody has disowned me!
One last suggestion: If you invite somebody (by text is great in fact - a simple message without room for elaboration) to meet you somewhere you wouldn't normally meet and say you want a chat, or there's something you want to talk about.. Assuming you don't often do that, that can be a bit of a heads up, and if someone clocks onto it they start imagining a scenario in which you're going to tell them something important like "I'm gay/I'm pregnant/getting married/dying" or perhaps even "I'm trans" (though a less jumped-to conclusion). They then get some time to think about how they'd feel if you did say any of those things, and the whole thing usually goes smoother.
I leave you with some coming out bloopers [Coming out usually doesn't go to plan]:
- Me failing at coming out as trans: "I've got something to tell you..... *huge pause in which I ponder bailing and eventually decide to say:* ... I'm.. pregnant..?" That really confused things. >_>
- I nearly missed New Year 2010 while coming out to a friend at a new year party.
- One friend's response to me coming out to him, while in a gay bar... "By the way, when you get a penis, you're f**king me with it first. Deal?"
- I literally have no recollection of coming out to one particular friend, who insists we had a really long and interesting conversation about it. I was pretty hammered that night. :S
- My uncle phoned my mobile phone from Iran a few weeks ago, trying to get in contact with my dad. This is an uncle that I've never met or spoken to before, and who doesn't speak good English.
"Uh hello is Morgan there?" "Yeah that's me, who's this?" "Um no I'm looking for Morgan [Second-Name]?" "That's me.. Who are you?" "Is your dad [Dads Name]?" "Yes..." "But, you're a man..? I'm [Name], I need to talk to my niece.." So at this point it was too late to suggest he had the wrong number. I tried to explain to him, it went something along the lines of: "...Um, ok. So, I'm not your niece any more, now I'm your nephew." "What?" ".... I'm transgender" "What?" "Transsexual?" "..... Ooooooohhhhhh, I get it I think! How long have you been a man?" And we ended up having one of the most odd phone conversations I've ever had.