pathfinder 1e – What and how should I tell about haunts to my players?

Haunts lot of details about them, such as specific weaknesses, ways to permanently disable and details about doing damage to them with anything that damages undead but heals living, such as lay on hands, channel energy or cure spells.

Which details should my players know automatically, and which things should be done part of a “mystery”?
How do I present this info if I want it to be more mysterious?

Haunt rules