From Longman Dictionary of Contemporary Englishmake it a rule (to do something)make it a rule (to do something)USUALLYto try to make sure that you always do something I make it a rule never to mix business with pleasure. → rule
Examples from the Corpus
make it a rule (to do something)• Since I have made it a rule not to lie to a client, I assume reciprocal honesty from him.• In fact, he made it a rule never to make any friend who could not be useful to him.• I make it a rule not to take friends on as clients.• I make it a rule to go at least three times.• They made it a rule that she was never to be alone. 