Parenting young children is hard, but incredibly rewarding. As a father, you have enormous responsibility: to model the fatherhood of God to your children, to guide their behavior through discipline and (what is infinitely harder) by example, to love them when they are least loveable. You must model those two attributes of God which are so hard to reconcile: nearness and authority, friendship and otherness. Your mercy must sometimes be severe, though you cry out against it. Your task is impossible, which is actually a comfort: If it were not so you might be tempted to think that you could actually do it. Instead, you just stumble along asking your children to forgive you when you fail and asking God to cover your mistakes.
The magnitude of your task bows your head in humility, but it does not crush your shoulders under a weight too heavy to bear. For your yoke is easy, and your burden is light. You have the enormous priveledge of watching a young life grow up and mature under your care. You see a new personality emerge, and you rejoice in every new thought, every new ability. Fatherhood spans the range of human emotion: joy, laughter, anger at defiance. Tedium as you correct a fault for the thousanth time, sadness when your child is hurt by the world you have brought him into, compassion when you hold him sick in your arms.
Along my journey, I've picked up some principles which guide how I try to raise my children. Caveat emptor: since I'm making this up as I go along, I don't really know anything about parenting children older than four. I should also mention that as a rule I don't pay much attention to parenting advice. Thoughtful and prayerful introspection on your child is worth more than a thousand books. That said, it does have its place.
One of the things I've been most surprised by is the degree to which children respond to consistent parenting. The "why can't my children act like that"? thought which every parent thinks almost always has a simple answer: it hasn't been important enough to you to instill that behavior. Of course children will fight you when you tell them to do something they do not want to, but if you hold your ground you will be surprised at how quickly they get the idea.
This has an interesting corollary: your children are probably not misbehaving for the reasons you think they are. This will make a big difference in how you react to them, so it's important. It's really easy to take defiance personally, as an affront to your authority. But children just want to know where their lines are and they will keep pushing until they find out. Young children do not listen to what you say. They listen to what you do. Instead of being upset that they ignore you, just follow through on your words with action and wait for them to get the picture. It doesn't take very long.
Rarely raise your voice at your children. As a tool for teaching them to behave, it is mostly useless. Children, remember, do not listen to what you say. You can't change this, so you might as well accept it and move on. If you yell when your children disobey you, they learn that they do not have to obey you when you use a normal voice because you never actually punish them until after you start yelling. Children are very good at finding out just exactly how much you will let them get away with. Much better for both of you to just give the command in a normal voice, and follow through if they disobey.
Yelling also gives your children control over you. If you show them that they can alter your mood by acting in a certain way, you give them a power that they should never have. Children manipulate each other like this all the time (cf. the sibling's smug, satisfied smile), and it weakens your authority to submit to it.
One more thing. Your children almost always understand more than you give them credit for. This seems to be especially true for younger siblings, because we as parents want to cherish their youth. Shoot over their heads by asking them to think about things that are too advanced for them and do things they can't yet. They will surprise you, and the effort is good for them even when they fail.
Young children enter the world as sinners. As soon as they are old enough to know you want them to do something, they are old enough to not do it. Like St. Benedict says of Abbots, our job as parents is more like caring for the sick than exercising authority over the healthy. But with care and love we can allow our children's personalities to bloom under the careful constraints of moral instruction, which makes them more rather than less free.