The "rules" governing the writing of vampires are extremely fluid. I can't think of a single other supernatural creature with as much variety or range. How they're made, how they behave, what they can or can't do--everything abut vampires varies from series to series depending on the author's preferences. This is why we have vampires creepy or hot, soulless or not, vampires that sparkle or brood. Even vampires like Jim Butcher's White Court who are born rather than made (if I'm recalling that correctly) and who don't drink blood at all.
When I started my Children of Night series (at the urging of my daughter who was frankly sick of listening to my complaints about the things I didn't like about other vampire series) I had to make a lot of decisions about what kind of vampires I was writing. Here then are some of my personal principles:
Principle #1: Scientific basis. The first thing I decided--and the guiding principle from which all the rest flowed--was that I wanted every aspect of my vampires to be something that could be explained by science--or at least psuedo-science--rather than being something that could only be ascribed to the supernatural. That means my vampires are fully visible in mirrors and on film, they are not adversely affected by religious icons or implements, they neither burst into flame or faint dead away at the first hint of sunlight, they do not need to maintain any connection to their native soil, and their aversion to garlic is purely a matter of taste. Though you'll never find it stated in any of the books, in my world new vampires are created through exposure to a parasitic organism that lives in the blood of other vampires. The reason it's never stated is that my vampires don't actually know that's why they are what they are. So shhhh! Don't tell them!
Principle #2: They don't rise from the dead. I didn't want to give up the undead aspect entirely, however my vamps don't die when they're turned. They do, however, fall into a comatose state (lasting for approximately three days) during which their bodies transform. This stage is marked by the cessation of most important bodily functions--heartbeat and breathing, to name two of them--and in the past could reasonably be mistaken for death. But as they say, what the caterpillar calls death the rest of the world calls a butterfly...or however it goes.
Principle #3: They don't age. Well, really, this one was easy. They grow older, of course, but their cells replicate EXACTLY with none of the mutations we call aging. In fact, the only change that occurs is that the older they get, the stronger and faster, more powerful and less vulnerable they become. That might be my favorite part. In my world, a really ancient vampire would be largely indestructible, which brings me to...
Principle #4: They die. Okay, look, it's pretty hard to kill a vampire--they aren't prone to human disease, they're faster, stronger and more resilient than humans, they heal incredibly fast--but it can be done. The world is a series of accidents waiting to happen. Eventually, everyone's luck runs out. Everyone's.
Principle#5: Vampires are made, not born. Actually, here's where I ran afoul of my own "rules" because while this is taken as absolute fact by my vampires--and it is mostly true--I do have a set of twins who were turned in vitro and were born vampire. It's never happened before...well, probably it has, there are legends, after all, but if it did, it was an unimaginably long time ago. And it's incredibly unlikely. I ascribe it to three factors. A, the twins were still mostly stem cells (which could adapt to become anything) when they were exposed to the vampire organism. This means their cells were able to adapt to the organism and force it to adapt to them. B, there were two of them, which strengthened the effect of factor A; and finally C, their mother never fully turned, so they were nourished with human blood right from the start.
Principle #6: They're not allergic to sunlight. C'mon, how's that supposed to work? Quite a few years back there was a movie and TV show about an alien race that had crash-landed here and managed to thrive despite the fact they were allergic to water. On a planet that's MOSTLY water? How's that gonna work? My vampires morph into nocturnal creatures when they are turned--that's why they mostly sleep during the day. They find bright sunlight enervating, they're extremely prone to sunburn and sunstroke, and yes, either of those could, conceivably, kill them. Other than that...no. Just no.
Principle #7: They drink blood. That one was pretty much non-negotiable. They are vampires, after all. But while my vamps need blood to survive, they don't need to hurt their victims. Vampire bat bites are painless and basically undetectable, after all, so why shouldn't the same hold true for vampires? They still have all the necessary equipment to eat regular food, but it doesn't nourish them and they don't need it. However...
Principle #8: They also eat cookies. Well, why not? As I said above, they get all the nourishment they need from human blood, however, they still retain some aspects of their humanity. So, yes, I have vampires who like to cook, who eat cookies and ice cream, who drink coffee, who basically, can eat anything they want. It just happens that one food they almost universally dislike is garlic. There's no accounting for tastes!
To learn more about my take on vampires check out this page on Amazon. It gives you links to all six Children of Night books as well as my short story, Blame it on the Voodoo, which is found in the Nine Nights in New Orleans collection.