Well; don't lie.. But accept that the truth might not always be obvious.
For instance, I usually play female characters online, because I'm more comfortable with that. Now; usually people don't ask me about my gender, and I'll talk about myself as a woman. Not really a lie, though.. It's not intended as such, and besides, I play a female character in an RPG. Role-playing game. It's also the way I feel, and since bodies hardly count for anything, on the internet.. No mirror-mirror on the wall telling me I'm hideous, see?
But if asked directly, which usually happens if people are... Interested, and want to be sure, I'll just tell them it's complicated. And then explain, if asked about it.
A few guys never wanted to talk to me again, one actually told me I should step away from all this, and live a good Christian life, so that God would make me a real woman after I die, and reach Heaven, and a few became even móre interested, and I had to fend them off by saying I wasn't single.
(Note: I do not play on U.S. servers.)
Anyway; when is it a lie to portray yourself the way you want to be perceived? And if that doesn't fit your birth-gender, then won't it always be a lie, no matter what you do? Won't HRT be a lie, since you're just 'taking hormones,' just like a cheating sports-jock? Will SRS be a lie, because you'll never have your very own ovaries/testicles?
Perhaps they are.. But they're the closest we've got to being who we feel to be, and what we so desperately wánt to be. Basically, they're the closest thing we've got to 'truth.'