How many staff members are at Hogwarts?

Answer 1

The is the Headmaster and the Deputy Headmaster.

Then the teaching positions are as follows:

1. Bathsheba Babbling, Ancient Runes
2. Cuthbert Binns, History of Magic
3. Muggle Studies
4. Transfiguration
5. Caretaker
6. Divination
7. Filius Flitwick, Charms
8. Care of Magical Creatures
9. Rolanda Hooch, Flying
10. Defense Against the Dark Arts
11. Irma Pince, Librarian
12. Poppy Pomfrey, Matron (nurse/works in hospital wing)
13. Aurora Sinistra, Astronomy
14. Potions
15. Pomona Sprout, Herbology
16. Septima Vector, Arithmancy

    I did not name the teachers in all the positions, as many of the positions were occupied by various teachers over the course of all seven books.

There are also many ghosts that reside within Hogwarts.. but when people in the novels speak of the ghosts at Hogwarts they are usually referring to one of the four resident ghosts of the Hogwarts houses -- Nearly Headless Nick of Gryffindor tower; the Bloody Baron of Slytherin; the jovial Fat Friar of Hufflepuffs; and the Grey Lady of Ravenclaws. -- each of whom, seem to work as a kind of adviser & help to the students.

Two other ghosts mentioned frequently are: Moaning Myrtle and Peeves, the Hogwarts poltergeist, is not considered a ghost, but an "indestructible spirit of chaos" according to Rowling.

And then there are the many house-elves, of course.... including Dobby & Winky.