My son is almost four.
Positive discipline: being respectful that my son is his own person--just as I am-- has his own agenda (which may or may not complement mine), and is bright enough to figure out why I need his cooperation through my asking questions, rather than always giving orders. (Whenever possible)
When he looks like he's about to do something unsafe, dangerous, etc., I often ask him a question first. "What do you think will happen if....?" " Do you think it's safe/unsafe?" "Do you think so-and-so will like if you do such-and-such?" "If you do X, what will we need to do?" " What can you do instead?" "Wow, how do you think so-and-so feels because you did such-and-such? Let's look at their face/check in." (empathetic approaches always enlighten)
I like to take a joint problem-solving approach when I can. It's not always possible, and I like very logical consequences when I don't receive cooperation. One example: If my son is trying to play when it's time to go to preschool, I remind him "You have just one more minute to get your coat on, or we will have to hustle, because we can't be late for school." He *hates* hustling, and as we walk to school, this is a natural consequence. We must be on time, that doesn't change. What changes is *who* is inconvenienced.
I will suggest a book: "Taking Charge: Loving Discipline that Works at Home and at School" by Joanne Nordling. I love this book, as do many of my teacher and parent friends.
And yep, our kids can *always* be better behaved. It's a sign that they have their own mind, when they don't always behave. I'm learning, constantly, to choose what's really important and to try to say 'yes' whenever it's reasonable to do so. We can discipline to death (read: punishment) and not get a 'better' kid. I try to work with my son's abilities and have reasonable expectations while giving him room to be his own person and to grow. I want to honor his whole person, and try to look at his challenges with this 'whole picture' perspective and not just focus solely on behavior. It's all entwined.
I understand, too, that every child is different. This is just what works for us.