• You do me a favor — I owe you one next time. 
• You say, “thank you”— I have to say “you’re welcome.” 
• You send me an email— it’s rude not to get back to you. 
• You follow me — it’s rude not to follow you back. 

But then, well-meaning people say, if you're going to be in the music business, you have to read this book on music business law, you have to learn networking skills, marketing, tech skills, accounting, and writing good newsletters, and so on.