The Directions you have there are good if you get a vampire hunting quest from some run of a mill peasant, but if you get a vampire hunting quest from a Lord, be prepared for a lot of searching around. I will assume that your Vampire isn't hiding in the Sewers, Crypts, or Dungeon (since if they are then you need to search in those areas for him. Now, for the two different types of ways to get the quest:
From a Peasant (like a regular Bone Carver or Weaponsmith) -
1. Simply get the quest and proceed to the town said Vampire is in. (Skip this step if he is in said town)
2. Talk to a Peasant in said town and he should tell you about the infiltrator, and the direction/shop/house to look in. (Skip this step if he doesn't give a direction)
3. Talk to Peasants along the way until you reach a house where they don't give you a direction/shop/house to look in. At this point, note the name of the Vampire.
4. Scan the room for flashing icons (at least in Ironhand or Phoebus Tilesets). Talk to them and see if the name they give you matches up with the Vampire. *Note that some might just be Warlords or Lords*
Bonus. If the name is the same as the Vampire, and is a Soldier type, abandon the quest of killing him. Recruit the Vampire Soldier into your Party instead (never accuse him of being a Vampire). You will now have a far stronger soldier who won't drown in rivers or sewers, will be ignored by the undead, and lots of other nice stuff.
5. If name is the same as the suspected Vampire, accuse him and he should tell you to prepare to die.
From a Lord (Guys in Forts, Keeps, and so forth) -
1. Simply get the quest and proceed to the town said Vampire is in. Remember to note the name or review it in your quest log.
2. Search house to house for flashing icons. Talk to them to see if their name matches up with the Vampire.
Bonus. If the name is the same as the Vampire, and is a Soldier type, abandon the quest of killing him. Recruit the Vampire Soldier into your Party instead (never accuse him of being a Vampire). You will now have a far stronger soldier who won't drown in rivers or sewers, will be ignored by the undead, and lots of other nice stuff.
3. If name is the same as the suspected Vampire, accuse him and he should tell you to prepare to die.