First impressions are everything, or so they say. When you apply for a job, you are supposed to dress nice, show what would make you a model employee, and otherwise be a pleasant person to be around. When meeting a person for the first time, you should be friendly, smile, and shake their hand with a firm grip (but not too firm).
In baseball, you should probably not do what Andrew Cashner did in his first start against the Blue Jays. Luckily, I think we’re pretty forgiving, all we ask is he not repeat history against the Orioles.