My policy with front line staff, CBSA personel, CATSA, etc... is always to be pleasant and accommodating. Besides being the right thing to do, I find this vastly eases the trip through the airport. If all hell is breaking loose at the airport, and you're that one calming, pleasant person in the crowd, the person helping you is far more likely to go the extra mile for you and/or spend more time with you since it gives them a mental break from the chaos around them.