I have to admit that the voice came easier to me than most... I've always done impersonations and character voices so crossing into female only took a few weeks to find and a few months of practice to perfect. For what they're worth, here are a few things I figured out...
-- To find your voice you have to figure out where the voice comes from... It's an actual location... Your natural female voice is higher in your throat and farther forward than your male one.
-- Try to impersonate cartoon characters... I found that Spongebob and Bart Simpson originate from the same "place" as my voice now. Once you find them, it's easier to find the girl :-)
-- Men resonate from their chest, women resonate from their head.
-- There's a CD by Melanie Anne Philips that I found helpful, although not revolutionary.. it's about $10
-- Don't give up! It takes most Tgirls months of practice to get it.. I practiced every time I was in my car. I would pretend I was having a conversation, having to explain all I knew about Transsexuality to someone who knew nothing. ANY GENETIC MALE CAN DEVELOP A FEMALE VOICE but it's an unnatural thing to try and get your body to do it. It's hard but KNOW that there are thousands who've done it and you're no different.
-- Several weeks from now, you'll be practicing and then it will suddenly hit you that you found it! It's a magical moment... After that you can ditch "his" voice forever