Leave it better than you found it
Continuously improve the product, the codebase, the processes, the culture. Work such that others appreciate that you were there. “Not my job” is like not picking up litter. While fixing a particular thing may not be my job, finding a fix and fixer is.
Treat coworkers like customers
Everyone deserves a good user experience. My output results in two products: one for the customer, and one for the coworker. The customer product is the “Product”. The coworker product is engineer-friendly APIs and code, audience-specific documentation, patience, mentorship and support.