Customer service is always very important to you, is it not? If you buy a $1,000 computer and the company tells you to go screw yourself when you have a problem and they won't let you return the computer, how would that make you feel? Pretty bad, right?
The concept of going the extra mike means that if you either own your own business or work as an actor, you should still be willing to go the extra mile to make the people you work with happy.
Think about it like this. If you were a director, trying to manage everyone on set and having problem after problem, and your actors all expected you to fully cater to their needs and wouldn't help you out at all because they know it's not customary to do that, things would be pretty normal.
BUT. Imaging you are that same director and one of the actors kept offering to help out and was being really nice to you. How would that make you feel? You'd remember that actor and really want to keep in contact with them and spread their name around, right?
If you go that extra mile to really try to lend a helping hand (unless you are specifically asked not to), you will much more likely be remembered in the future. Your "customer service" of sorts will be so much higher than that of other actors.
Think about it, then put it into practice.
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