Level 1 (Graveyard)
Drop bombs as many as possible.
Level 2 (Cave)
When he is stalking around you, whip or mace his head.
Level 3 (Banquet Room)
Boss: Stainded Glass Knight
If you have Holy Cross and Sword you can beat him easily. Be care when he jumps and walk under him only.
Level 4 (Basement)
Boss: Stone Golem
Use Watch or Holy Cross. Jump when he attacks you, you will receive damage anyway but it should be less than what you deal.
Level 5 (Clocktower)
Use Holy Cross. Watch out when he hits the wall and drops giant blocks above you. Fortunately, he is chained.
Level 6 (Vampire's Castle)
Boss: Dracula (Human Form)
Use the Holy Cross. When he transforms into bats, crouch at the middle of the screen.
Boss: Dracula (Giant Form)
Use the Holy Cross two times against him.