Dealing with Fangirls
Or, stay away from that dead bat

1) There are fangirls, and there are "rabid" fangirls.
Some fangirls are normal people who just happen to really like a certain subject or genre. They live among us, and you would never know unless you got them in a deep conversation about their chosen topic.
However, there are fangirls that are completely rabid about their object of obsession. They will mention it at every opportunity, and even work it into a casual conversation about something completely different. They make it incredibly clear that they are obsessed and going to stay that way. These are actually a minority, but are so loud and obnoxious that they are what is always seen by the public. Oh, and they're proud of it, too. This is the stereotypical fangirl, and should be feared.
Learn to tell them apart.

2) Avoid the rabid ones.
They will only make you feel awkward, depressed, or frustrated.
About 75%-90& of their lives is focused on a single subject, and if you happen to be a normal fangirl, you'll be weirded-out that they can spend so much of their time on it. If you aren't a fangirl at all, you'll probably be running for the mental hospital, screaming all the way there. It takes a very delicate and diplomatic person to correctly steer the conversation -- and the results can be disastrous.

3) Never, EVER insult their object of affection.
This one mostly applies to the rabid fangirls, normal fangirls will not be quite as offended, and may not even mention it.
This one applies especially to rabid yaoi fangirls. If you don't want to be attacked by paddles and called a homophobe, don't insult the gay.
You'd think that the rabid fangirl would just leave you alone to wallow in your uneducated-ness, but this doesn't happen with the loud ones. They will argue constantly, consistently, and continuously, until your sanity has fallen and you just want it to stop.
(This is often a way to tell normal fangirls from the rabid variety, but be very, very careful, lest you are attacked by a mad horde of angry rabid fangirls.)

4) If you're a good looking gay guy...
Don't go anywhere near the rabid Yaoi fangirl. You will be glomped into oblivion, and may the Flying Spaghetti Monster have mercy on your soul once this happens.

I consider myself a "normal" fangirl, and all of my friends have instructions to shoot me if I ever become rabid. If you see any of your normal friends infected by the rabies fangirlus virus, stop them before it's too late.