There has been a great deal of discussion on how parents are trying too hard to be friends with their children and how that is detrimental to the family relationship. I believe that you must be both. Your children should truly understand that you are there for them in thick and thin. They should know that you are open to discuss anything that is truly bothering them or that brings them great joy. You should enjoy fun times together and great laughs.
They should also understand that certain rules apply in your household and when broken punishment will be given. Punishment can be as simple as a reprimand or a bit more serious like time-0ut but during this entire process they must know that you do this because you love them and want them not to be hurt or fail in the future. If punishment is threatened but never given or lightly given, then it becomes a white line that erases like chalk and you will not be taken seriously
Parenting is a tough balancing act if you are too strict your children might fall off and fear telling you about it but if you are too lackadaisical they might continue to slip and eventually fall to far for you to catch them. It is a challenge that requires continual evaluation of yourself and your own techniques in communication. It also requires you to watch and learn from others that might have different experience then you. Parenting like most life experiences is something you will continual review and improve over time.