Determine the genre of your vampire story. Although it may blend elements from several genres, what is it, primarily? Once you've determined what kind of vampire story it is, determine the focus of your story. For example, if your story falls primarily within the mystery genre, and the focus of your story is the unexplained deaths in a small town, the title should inspire a sense of drama -- will the intrepid heroine discover the truth, and if so, will she survive herself?
Narrow the focus further. Determine the tone of your narrative. If your story is within the action genre, an fast-paced monster hunt like the original "Dracula," the mood may be tense and dramatic. This, too, should factor into your choice of title, which should convey the heroes' race against the clock as they rush to outwit a crafty opponent.
Use a thesaurus to compile a list of words that most nearly convey the genre, focus and tone of your story, then experiment with combinations to test which convey that meaning best. For example, any number of vampire story titles might use the words "blood." However, the combination of words makes all the difference. Compare the fictional mystery title "Blood Hunt" to the fictional suspense title "Night of Blood."
Get feedback from friends as to which titles, among several possibilities, they find most compelling. Study the titles of successful vampire novels and take note of which ones tempt you to pick up the book and start reading -- and why.