Most Vampire myths come to us from the Dark Ages, when science was in its infancy and people looked to religion or superstition to explain the world around them. While many Vampire myths have their basis in Christian orthodoxy, others represent imaginative interpretations of actual Vampire behavior.

Vampires sleep in coffins

Source: this myth probably arose from gravediggers and others who observed vampires emerging from coffins and crypts.
Truth: if a vampire did spend the night in a coffin, it probably had nothing to do with sleeping preference. In the old days, many victims of Vampire bites were interred while still in a Vampiric coma. The truth is, vampires will sleep wherever they feel safe.

Garlic repels vampires

Source: most likely based on observation.
Fact: Vampires have sensitive noses and can momentarily be driven off by pungent odors. However, this method of deterrence is unreliable and certainly won't work on an experienced vampire.

Crosses repel vampires

Source: Christian religion.
Fact: crosses have no effect on Vampires.

Vampires are killed by driving a stake through their heart

Source: Christian religion.
Fact: because their blood is circulated by skeletal muscles, vampires can easily survive injuries to the heart.

Vampires burst into flames upon exposure to sunlight

Source: most likely based on observations of a vampire's extreme reaction to sunlight
Fact: sunlight renders Vampires, with their hyper dilated irises, blind. It also causes neural pathways to fire randomly in the Vampire brain, creating an extreme epileptic reaction. As dramatic as this reaction may appear, it will not be enough to start a fire.

Holy water burns the skin and flesh of vampires

Source: Christian religion.
Fact: holy water, or any water for that matter, has little effect on Vampires.

Vampires prey on virginal women

Source: a reflection of Victorian-era fears over the sexual awakening of young women.
Fact: while Vampires have a stated preference for the taste of young blood, they are not particular as to which gender provides it.

Vampires can fly

Source: observation of leaping Vampires; association of Vampires with bats.
Fact: while they do possess extraordinary leaping ability (Vampires have been observed leaping over fences 20 feet high), Vampires cannot fly.

Vampires turn into bats

Source: association of Vampires with bats.
Fact: no,Vampires cannot turn into bats.

Vampires are not visible in mirrors

Source: Christian religion. It was thought that a Vampire, or any creature lacking a soul, would not produce a reflection in a mirror.
Fact: Vampires are visible in mirrors, although interestingly enough, they are often quite discomfited by their own reflections.