One of the advantages vampires have over certain other undead beings is their ability to pass as humans and go undetected. Whereas a zombie might reveal himself when a rotting finger dropped off, and a skeleton would be hard-pressed to explain his lack of flesh, nosferatu in search of prey can walk through the streets of towns and cities until they find a victim. Thus vampire slayers have created arcane eyepieces which will reveal those creatures of the night, without the need for less subtle methods such as splashing holy water on passersby or -- worse yet -- the experimental plunging of stakes into hearts.
The best vampire slayers are sometimes vampires themselves, who use their enhanced speed and strength -- along with their understanding of how nosferatu think and hunt -- to stalk their malevolent kindred.
"Of course she was a vampire! She died when I stuck a stake through her heart, didn't she?"-- A vampire slayer, on trial for murder
A vampire slayer once tried to stake Katrina von Malhaven at a ball. She responded by knocking the weapon out of his hand, grabbing him by his ankle, sauntering over to the balcony, and holding him upside-down over its edge. The vampiress proceeded to give him a long lecture about he churlishness of attempting to slay vampires indiscriminately. Either because of the blood rushing to his head, or because her words had brought him to a better way of thinking, the fellow agreed to mend his ways. Thus Katrina drew him back to safety, deposited him on the balcony, and returned to the dancing.
Vampire slayers are all well and good when they dispatch murderous vampires. However, in one city the vampire community proposed that there should be vampire slayer slayers, to hunt and kill those vampire slayers who slew innocent vampires. Those hostile to the undead countered by suggesting that were this to take place, the city must also institute vampire slayer slayer slayers, lest certain vampire slayer slayers begin a campaign of wanton vampire slayer slaying. The two camps argued back and forth for some weeks, until they each ran out of ink and parchment due to the sheer number of times 'slayer' had to be written in each of their official petitions. At that point they agreed to reach a compromise.