Evidence

Ghosts can have 2 - 5 evidence (depending on which difficulty), EMF can go from 3/4 - 5, Entity scan can show multiple scan codes, The spirit could communicate through the EVP which is the spirit talking through the spirit box using words, it can communicate through the Radio which is just a radio through the spirit box, or it can make a noise which doesn't come from a spirit box. Ghostwriting can either be on the book (when you ask it) or on a wall somewhere, it could appear as words or drawings. Sometimes the wall drawing or writing can only be seen through the photo camera so be aware of wall writing or drawing. Temperatures can be measured through the MEL or the Temperature Reader, you go up to the ghost and see if it's either negative or at zero.
Based on evidence you will get different exorcisms to get rid of the ghost. It's always constant e.g. when ghost has negative temperature you will always have to use Incense on the Dread origin of the ghost.
Some ghosts (Revenant, Shadow, Poltergeist, Demon) add their own exorcism - this is also constant. E.g. Shadow will always have to be flashed with Instant Camera. 
(
Bear in mind the infestations (Flies and Cockroaches) are not included in the table. You'll have to Incense the Flies and use Neutrino gun on the Cockroaches.)