Great onboarding book by Intercom summarized:
A successful onboarding flow is not about cheap and quick wins like changing the colour of a button but about enabling the user to experience the magic moment faster. That is what turns them into loyal customers.
Understand functional personal and social goals. Onboarding is not a one time function but a continuous process throughout lifecycle of the product.its about changing people’s behaviour. Your users are frustrated doing something & are hoping to do it better,make sure you show that.