I haven't seen one. Where the heck are they?

In Downtown. They come out every night there. If you wanna be one, seduce the Grand Vampire.

I'll just try harder to find one. Thanks.

They're hard to miss: Look for the goofy characters with blue skin (unless you used a vamp default replacement) and old-timey Dracula gear, covering their faces and hissing at people.

Yea, they are hard to see sometimes. Also, keep a look out for flying bats. If you see one, you've just seen a vampire :D

Well maybe since it's at night... And I don't know whether the frequency of their spawns is set for certain locations, but I've found mine visit that one gothic dance club the most. Go figure, right?

They hang out at whichever Downtown lot you visit the most. (They also tend to wait until someone who is never supposed to meet one is on the lot rather than showing up immediately for the person you send Downtown every night looking for one.)

they are always at the crypt o night club downtown.

I always seem to find them at the LuLu Lounge, personally; even when I first visited.

If you're not against cheats and mods or whatever, you could also look for and get a mod that will make your character a vampire without needing an actual vampire npc there. (I can't remember where I saw it but there's a painting here or somewhere else that you can change into or cure yourself from a creature form like the vampire) Strangely enough, I often find vampires visiting my laundromat community lot. Sims vampires are so much weirder than other vampires. The goofballs. Hahaha.

http://www.parsimonious.org has potions you can use...

Look at the Crypto Nightclub and Rodney's Hangout for the Male Master Vamp and Bernies Botanical Dining and any of the bowling alleys for the Female Master Vampire- she is usually blond or black haired and wears a red medieval dress- he is usually dark haired and skinned or pale with red hair and wears the traditional type Dracula costume from the movies. Sometimes there will be more than one if you have up to FT and have not patched because the NPC service Sims like the master vamps and high witches tend to spawn- extra male Master Vamp usually hangs at the culinary hobby lot and the extra female Master Vamp hangs at the films and lit hobby lot - at least in my game.

I never see male Grand Vampires - mine always seem to be female. And how come all female vampires are called Contessa? Really?

That is EA being silly and cliche'. The males are all Count Something. And the redheaded one has Benjamin Long's nose. (Actually Kennedy Cox has the same nose as well.)

Found one. Somehow, I'm pretty sure I hadn't seen one before then. Ah well. Annoying to befriend, I have to say.

Thanks people. ^^

Wouldn't it be easier to use boolProp, then go to Spawn -> Sim Modder and turn into a vampire that way?
I know people don't like to use boolProp, but it's easier than downloading custom content, installing, hoping it works, et cetera.