golden rule 
noun
1A basic principle which should always be followed to ensure success in general or in a particular activity.The North West Coastguard advises anyone venturing in to the Bay to follow the golden rules to ensure they do not become another victim of its treacherous sands....
- There are some golden rules to follow when choosing a hat.
- Those are two basic golden rules, and they appear to me to be a matter of logic.
1.1The biblical rule of ‘do as you would be done by’ (Matt. 7:12).We've still got church and sacraments, after all; we've got scripture and prayer; we've still got the golden rule and the Ten Commandments....
- This could include everything from telling the truth, fulfilling commitments and promises, and treating others as you would like to be treated; in other words, the golden rule.
- What Rachel teaches us is the virtue of following the universal golden rule - treat others as you would want others to treat you.