That may seem like a wise-crack, but it's also a correct answer. Unlike other subcultures, Goth is not defined by necessary and sufficient characteristics, or by specific common interests or fashions or goals. There are common tendencies, such as wearing a lot of black and listening to music from a genre called Gothic, but no sharp definitions. Goth as a subculture began with Gothic music, and the music is still a very important part of the culture, but it is no longer a defining point.
We do not choose to become gothic, we discover that we are gothic. We come together into our own little subculture because no other subculture would have us.
That makes it very difficult to understand what Goth is about from the outside. The best way to learn what it means to be Goth is to look at a lot of examples, which is becoming much easier now, thanks to the Web. Many Goths have a good amount of technical skill, so a lot of us have web pages. And we tend to be very close-knit, so once you've found one (and if you're reading this, you have) just follow the links to hundreds more.
Looking at our creations, you'll notice a consistency. It pervades our humor, our music, our dancing, and all of our arts, ranging from the abstract beauty of physics, math, and computers, to our more tangible and equally beautiful poetry and prose, painting and drawing, sculpture and digital rendering. This is the thread that ties us together. This is the dark aesthetic.
The only other defining characteristic is this: Goth is weird. That's one of the things we like about it. We refuse to be normal for the sake of fitting in with popular society. Since non-Goths generally don't understand what Goth is about, they draw inaccurate conclusions and imagine connections that just aren't there. In this manner, the Gothic community gets connected to all kinds of other poorly understood phenomena, particularly if there's any visual correlation that appeals to common sense or mass-media saleability.
Goths tend to wear black, have pale skin, and go out at night. That's as close to "vampire" as most of us ever get. A few of us like to dress up as vampires when we go out. We do not think we are vampires.
We appreciate and often try to emulate the mysterious, dark sensuality and romance of the mythical vampire. But that does not include drinking blood. There are a very few who do, just as there are a few radicals on the fringe of any group. But even they do this only between consenting adults, in the privacy of their own homes. When the news media finds some mass murderer wearing black and drinking blood, they invariably point at us. Those psychos are not Goth, they're just insane.
A lot of us read Anne Rice, but most of us have an insatiable appetite for good literature, so there's not much we don't read. A fair number of us like to indulge our imaginations in role-playing games, one of which happens to be White Wolf's "Vampire: the Masquerade." You don't have to be Goth to play V:tM, nor do you have to play V:tM or read Anne Rice to be Goth. There just happens to be some overlap.