I think mine is actually that if there are rules, they should be written or codified somewhere! Strong communication and making no assumptions about what makes sense to other people I think is a must when working on a development team.
Corollary: a colleague will /always/ forget something important when communicating: most likely because it's the context of their issue and they are inside it. Be prepared to live in the dark for a while as you politely ask for explanations and they surface from their silo... sometimes resolving stuff in the process (hello Rubber Duck debugging!)
Oh, yeah, being prepared to ask questions and walk through stuff with people is like a real key underrated dev skill.
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