Well .. funny you should ask. There are 3 noted ways in the Vampire Scriptures and Lore. You can BE BORN A BLOODSUCKER. You can be BITTEN unwillingly (or willingly in the case of my ex) or by death…
Vampires as have been noted, feed on human beings, not pastrami sandwiches as one marketing rep of a Kosher Bagel shop in my neighborhood would like customers to think. A vampire bites the person in the neck, as far as we know, as when the first vampire movies came out, it was a very PG rated place to place an unlikely bite.
That person, as a result from the bite becomes one of the undead themself, a great club to belong to, but at a very high membership price, your mortality.
Now, what scares the bejesus out of Vampires? Some of my garlic, encrusted Italian relatives have no fear of Vampires. Matter-of-fact, my aunt from Italy dusted under her armpits with fine garlic powder on a daily basis (Believe me, it was an improvement).
Vampires shy away from Religious talk (or maybe they just are bored with boring sermons).
Vampires sleepwalk, have bad hygiene (heck, they only have one pair of clothes and sleep in the same worm-infested crypt for centuries), have foul breath and they are whiter-skinned than an Albino Mudslapper.
A child can be born (according to lore) a vampire by being born on a holy day, a new moon, equinox or being born with a weird attribute, like an extra nipple in the middle of their forehead (hey, don’t laugh, I know some guys that would probably be into that). Some say, if a child dies before Baptism, it is a sure indication. Or being born the seventh son of a seventh son. A good and reliable sign that a child has become a vampire or soon to become one, if the child rips mom’s jugular vein open during breast feeding .. although some dentists claim that could just be related to ‘teething’.
In Romania, home of many thirsty bloodsucker reincarnates, they believe burying someone face up will result in them returning as a vampire. My aunt matter-of-fact, was so mean in her life, my uncle buried her face down in the unlikely event she’d try to dig her way up. He said, “This will ensure, the more she digs, the deeper she gets.”
But then again, all this is lore and probably myth. I have to go now. It will soon be dawn and I have to return to my children of the night … and sleep.