My children are now seven, five, two and seven months old. My first three kids are already being taught manners and rules as early as two years old. They are appreciated for good behavior and reprimanded for bad behavior. Sometimes, a spank on the hand or on the butt is given when necessary. Some people would say this is too early. For me, these ages, 2 to 6 years old are the best time for instilling discipline in children.
I am thankful that my husband shares my disciplining principles. We also do not contradict each other in front of the children when the other's act is not entirely to the approval of the other.
One thing that has proven to be really effective is being consistent. Being consistent means sticking to a principle or upholding a rule no matter what. This sounds like military training but it isn't as harsh as that. It's simply being consistent. If you tell your kids that watching telenovelas is not allowed for them, then it must be the rule at all times with whoever is watching over them.
One thing that also spells consistency is not talking about your children's not-so-cute antics in a way that would seem like you are actually proud of what they did. You always see this. Parents talking to their friends with the kids around and the topics goes around to something your child did that was a little bit nasty but cute. For the child, this means "Oh mom sounds like she is proud of what I did."
Consistency in disciplining need not be all reprimand. Most of the things we need to teach our kids are those that we need to remind them everyday. Put your clothes in the hamper, finish your food, don't watch tv while eating, put your shoes in the rack and that sort of stuff.
Remember, kids who are taught good values basically carry these on to their adulthood. If they become well-mannered individuals, they will make you proud.