Phone interview to begin with, basically they are looking for someone who can hold as casual conversation. Don't try to impress them, be yourself and answer the questions honestly with enough information but not too much.
Next you'll have an interview in the office, wear nice clothes. Button up shirt and slacks for the men, no need to wear a tie or suit unless going for management. Be on time. Greet the person with an interview and a smile. You will be asked if you can handle the BORING job and being YELLED at, be prepared to answer that.