Argh

Why do vegans have to act like assholes so often? The message is extremely important, don't shoot it.

When people are asking questions, don't attack them, don't put them off. Encourage them.
Let people be imperfect.
Don't come across as obnoxious or holier-than-thou.
Be nice and down-to-earth, don't act like you're better than anyone else.
Don't reinforce negative stereotypes.
Don't use provocative and highly negative words ("meat is murder", "so you enjoy eating corpses?"), because when you do, the other person is going to focus on those words instead of the important message.
Even if the other person is acting like a fucking asshole, be respectful towards them, and it's very possible that they will stop being a fucking asshole and start listening.
Create a conversation, not an argument.
Don't be PETA, don't come across as sexist or racist or extreme or crazy.
The animals come first, moral purity and ideological perfection are highly secondary.

I know it's difficult because you're human and humans are irrational. But really, when I look at the animal rights movement I often think that the animals deserve something much, much better than this.