Hiring a new staff member is a tricky and potentially very costly exercise. The wrong person might be quite capable of doing the job, but might cause divisions amongst the staff. Or might not be up to scratch where the work is concerned, but gets on very well with everyone. Both of these are appointment failures.
Good questions to ask when interviewing new staff
What sort of salary were you thinking of?
What are your weakest points?
How do you get on with people generally?