The 60s generation lost the concept that authority is a good thing. Authority is essential to maintaining order and structure in a family. The boundaries are known and the child does not have to continually test them, leaving energy for more productive activities. Mean what you say. Don't allow guilt to cause you to back down on what you know is right.
Many parents underestimate their influence over a child.
With a good relationship, the child will come to you when they need to. With a good parent-child relationship almost any form of discipline will work. With a poor parent-child relationship almost any form of discipline won't work. Respect your child. Treat them at home as you would in front of others.