HBR’s summary article on the importance of getting a cultural mentor when joining a new company:
We often assume that if we’re successful at one company, we’ll easily succeed at another. But it can be jarring to join a new organization with a very different culture. One way to ease the transition is to find a cultural mentor: someone who can help you interpret and navigate the implicit codes of the new culture. Look for a person who has a deep understanding of your new company, wants you to succeed, and doesn’t have an overt political agenda that could cause them to give you biased information. This might be a former employee you know through social or professional circles, or a respected colleague in another office or department.
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Observe the nuances of your new culture carefully to ensure you don’t repeat your mistakes and damage your ability to succeed at your new job.
Full article: Dorie Clark’s “Navigating a New Job with a Very Different Culture”