There's a variety of factors which would make a good interview or not. Simply put though, the interview is designed to suss out the things which you can't get from an application form or a resume, and is meant to simulate a typical scenario when you are dealing with clients/team mates/partners/etc. If you are able to prove you are capable of communicating effectively, learning, working as a team, being positive, listening, etc... then you'll most likely do well. Of course in a one on one interview, the quality/content of your answers is also important too, but it's the way you deliver it which can make or break.
As for pay, it's in the low 30's depending on firm but if my time is anything to go by, mid-tiers pay considerably higher. That being said the big 4 offer you better career progression prospects (both within and external to the firm), and nowadays even offer better leave entitlements (most if not all the big 4 now offer 7.5 hours/1 day of study leave per week during semester).