I have heard stories of certain airlines encouraging their pilots to skip de icing queues and take off with a little bit of ice on the plane,unless it is absolutely 100% necessary,rather than as a precaution, in the name of saving a few hundred quids worth of fuel. Such actions may be viewed as professionalism from a purely commercial perspective however from a flight safety perspective are criminal.
therefore i reckon professionalism is amoungst other things putting flight safety first, before commercial and personal considerations. That and getting to work on time, in a fit state to concentrate 100% on the job, neatly dressed, and you can't go wrong. In essence you need to behave a the manner which the couple of hundred people sitting behind you would expect you to.
I reckon though that a pilot should only be expected to behave professionally whilst on duty, they are normal people and are entitled to do what the hell they like at other times, id imagine a lot of people would be shocked if they knew what their pilot got up to outside of the plane!