There's quite a variety of "causes" of vampirism in novels today, depending on whether or not the author is marketing the book as a horror novel or as a romance.
How To Become A Vampire:
a) Be cursed on someone's dying breath or by a gypsy. Vamps who have this happen to them have usually been around since the 1600-1700's.
b) Be bitten by another vampire, either as part of vicious attack (e.g. a pack of rogue vampires) or in attempt to save a dying person (e.g. the vampire's "true love")
c) Be infected by a genetic virus that mimics the standard symptoms of vampirism (allergy to sunlight, nutrients in human blood needed to either support the virus or control it). Not technically the undead, they can procreate.
d) Be infected with nanites initially designed to cure illnesses, but whose programming mistakenly viewed the normal aging process as "illness" thus keeping the host young. Because of the constant cellular repair, the host does not provide enough nutrition through its own blood, so human blood must be consumed to supplement its body's own process. Atlanteans are favorites for this method. Ditto retention of the ability to procreate.
e) Be cursed by a god or a goddess causing resurrection as a vampire after death. Usually happened to ancient Greeks, Persians and Egyptians.
f) Became a vampire as a deliberate choice.
Modern Day Vampires:
a) Either sleep like the dead during the day or else are able to stay awake but must be careful of the sun. They use a high SPF sunblock, hats, sunglasses and long duster-type coats when going outdoors. They drive in cars with specially-treated windows.
b) Can see their reflections.
c) Unless they became a vampire due to a curse, they usually retain whatever faith they started out with and can enter churches, hold crosses, etc. The exception are those vampires who had to die first to become a vampire - they usually can't go onto land or into places that are specifically consecrated against the undead.
d) Unless they are rogues or traditionalists, they usually get their blood supply from blood banks (which they or their Council usually owns). Bags of blood are popped into the microwave to warm up.
e) The undead type of vampires need fresh blood to create blood pressure in order to get an erection; not enough blood, no boner.
f) Holy articles and things like garlic have no effect on them.
g) They must be invited into a private home; they can enter public buildings without an invitation.
h) The virus-or-nanite infected vampires can eat and drink just like regular folks; body functions are about the same.
g) While werewolves tend to operate within a pack structure, vampires usually have a Council made up of really old, old vampires. Sometimes there is one over-arching Council, other times there are multiple Councils (North American, European, Asian, etc.). Vampires who don't obey the laws of their respective Council are usually deemed rogue.
h) Most vampire Councils have some sort of enforcer branch to eliminate rogue vampires or any vampire that is drawing too much attention from the human population.
g) They don't change into bats. Sometimes they have the ability to fly but the physics explanation usually involves "magic" in some way.
h) They are usually stronger, faster and have sharper senses than humans. Their ability to "disappear" is usually due to their super-fast movements.
i) They consider themselves the top predator on the supernatural food chain. Humble is not a word in their lexicon.
As you can tell, I read way too much of this crap.
