Communication, love, respect for each other and caring.
Don't sweat the small stuff and allow freedom for both parent and child. Listen to your child and carefully make decisions together if possible. Never yell, talking is important and discussions of issues should be applied with no effort. Be calm in all situations. Be confident, and positive. I have a son of 20 and id not have issues with him because I applied my own ways of parenting. Once your child shows responsibility that means they can be independent and cope with their own situations. Time shows you all. Be there for your child in any conversation to make them feel happy when sad, to make them feel stronger when they feel weak, to always help whenever possible but never interfere with their plans or decide for them