It may help to understand children's behavior as strategies to meet their needs. Pretty much ALL human behavior makes more sense when viewed this way, actually. But with very young children, their strategies are not usually too effective, and often seem confounding or infuriating to parents.
This is because the lives of most toddlers already contain as many negatives as they can reasonably be expected to bear. They have little-to-no impulse control. They are physically incapable of doing much of what they would love to do, they are prohibited from touching/handling a thousand desirable objects a day, they are repeatedly pulled away from activities they want to do, and seldom allowed to explore any activity to their complete satisfaction, they are scolded frequently, often for concepts they can't yet grasp, and they don't even have the language yet to tell their parents why this is all so exasperating.
With all that in mind, Dr. Harvey Karp of Happiest Toddler on the Block uses positive approaches to connect emotionally to a young child. They are strongly emotive little beings, and they feel real relief when an adult "speaks" to them in a way that takes their needs into account. Here's how Dr. Karp achieves this wonderful connection: http://www.youtube.com/watch?v=fJ1428uYs2g&NR=1&a.... .
Once children, even older ones, are sure they have been heard and understood, their stress levels drop and they are more able to take in what the parent is trying to communicate. Though I don't currently have such a young child in my life, I have gotten great feedback from parents of toddlers who are trying the Happiest Toddler approach. For somewhat older kids, you can continue this positive parenting with the brilliant techniques taught in How to Talk So Kids Will Listen, and Listen So Kids Will Talk, by Faber and Mazlish.