I agree with some of the previous posts:
A vampire DOES cast shadows and DOES reflect in the mirror. After all, he/she is still made of the same flesh and bone that they had in life.
A vampire can go out in the day, but night is usually a better time for them to do their dastardly deeds, and according to lore, night is the traditional time for them to come out of their graves.
The whole "Stake In The Heart" thing has gotten misrepresented over the past century too. It was derived form the belief that criminals and unholy people would come back to life after death, so they would nail the corpse to the bottom of the coffin (with a very large nail or stake), so that when the corpse came back to life it could not get out of the coffin, and thus would starve to "Death".
Also, they would behead the corpses to prevent it from coming back form the dead (which may be the ONLY way to truly kill a vampire!).
I would also eliminate religious symbols warding off vampires, along with the "Vampire can't enter your house until it's invited" thing.
I think the best thing to do is to read about vampire lore form very old books, ones that haven't been influenced by the past hundred years of novels and Hollywood. I have an encyclopedia set that's over a hundred years old, and it was very eye opening what the origins of vampire lore were about.
