They have good communication and keep us informed. Too many reps just know how to spend the money, not use it wisely. They put together amazing proposals and push the envelope. They respect the client and the agency. They are passionate.
Good reps pay attention to detail, get things done on time, and return calls.
Good reps are on time with their deliverables, within budget and are professional. They also have good reporting skills. A good rep is one who is a good listener and provides me with what I want on time. They follow up, but are not too pushy. They give me time to get back to them.