Getting to the sunken Citadel in the docks:
Go towards the store when you first arrive at the docks. Immediately after
you have passed the quarantine gate stop and destroy the box which is in
front of you. After you have gone down the ladder follow the stairs.
Defeating Keeper Guards:
To defeat the Keeper Guards use a mine or if sniping hit them in the back of the head. The Blackjack has no effect on them.
Defeating Zombies:
A single Flashbomb will kill a Zombie if it is unaware of you but if it is
aware you will need Flashbombs to defeat it.
Defeating the Undead:
Defeat multiple Hammer Haunts or undead on a floor by throwing Holy water into a doorway then luring them after you so when they run across the Holy water it will kill them.