Hi, Joey.
I came out to my parents after coming out to my school. I was out for a few weeks and had support from professors, staff, and new friends. Well, I didn't have their direct support; I just had the confidence of being Lyra around them and being accepted correctly about 90% of the time. Once it got to the point where I couldn't handle doing boy-drag anymore, I sent them an email explaining my situation.
They were....tepid. I think they are still struggling with it a lot and part of the reason is that we have a very complicated history. It's actually pretty upsetting so I might make my own post about it but I'll just say that I think the response was as good as I could have hoped for, given who they are and what lies between us. The tactic I used was to be as plain and honest as I could be: not asking for permission or apologizing, not making any accusations either, just explaining that this is what I am doing, and that I would be happy to answer any questions.
Of course, this wouldn't work for all parents. It really does depend on your particular family dynamic and lots of other particulars. I think you would want to talk with someone who knows your parents fairly well, if possible, and who will also be supportive. I'm wondering if telling other family members might be helpful; it seems like it is easier for them to be accepting and supportive if you aren't "their baby." Then you could possibly get their perspective on how to approach your parents? Just a thought, I fully understand it may not be practical since I haven't even tried it myself.
I have no idea if this would be useful for you, but I often consult Tarot cards for advice on situations like this.
And definitely check out the resources linked to above, I bet there's some good stuff in there.
My parents got really upset because they didn't completely understand some of the information I had told them, and thought I had done something really outrageous, so make sure you are crystal clear about what you tell them, when you do tell them.
Best of luck. We'll be here to help either way.
-Ravens