Reliable equipment, boat doesn't have to be pretty, but it does have to be safe.
Knows the river, and works for you.
Good rapport with clients.
Teaches me how to catch fish in a way I've never tried before.
Listens to the wishes of his client.
Gets the boat into at least one fish.
Brings the appropriate sense of humor for the crowd (eg. a plaid, a pink and a beige walk into a bar....)

This would be the minimum requirements, anything more would make for a great trip.