While I have, for years, considered myself an ally when it comes to LGBTQ issues, I have had very little personal experience or even exposure to transgender persons, and as such am woefully uninformed. Luckily, there are many wonderful people online who take the time to educate and eradicate misinformation.
Skepchick (Y'all read Skepchick right?) has launched a new sister site, Queereka with a focus on Skepticism as it relates to the LGBTQ community.
Natalie has written an incredibly informative article on the misconceptions surrounding trans women that is well worth the read.
13 Myths and Misconceptions About Trans Women: Part One
13 Myths and Misconceptions About Trans Women: Part Two