I have found that I have to teach my children how to cope with frustration and hurt feelings. When someone causes a physical hurt, hurts their feelings or they can't have what they want and are frustrated, I take the time to teach them what to do instead. I tell them they need to use their words and tell me (another adult or the person that hurt them) what's wrong. They need to learn to vocalize why they are upset, in a nice tone, without bursting out and hitting. If they hit someone, I tell them that when someone hits him it really hurts. We don't like it when we are hit, so we shouldn't hit others. I might lightly tap his arm or bottom and then ask him if that was nice and show him he doesn't like being hit either. I make them say "sorry" and give a hug to another person. Sometimes my boys will come up to me with an ouchy or hurt feeling and I console them with hugs, kisses and soft touches. I encourage them to see how I help them feel better and do similar things to others when others have hurt feelings or ouchies.
I show my boys how to resolve conflict by using words, asking for items, sharing, and taking "no" as an acceptable response. I ask him to wait instead of repeating the question, whining and throwing a tantrum. I tell him to be patient. If he doesn't comply, I ignore his episode and walk away. I don't give him the attention he wants from the tantrum. If he starts to whine, the response of "be patient and wait a few seconds" turns into a "no". If he whines or throws a tantrum, even if the request was going to be "yes", I say "no". I make him act correctly to be rewarded with whatever it is that he wants. I don't give attention or award poor behavior.
Timeouts work sometimes. But, for example, my son may decide he doesn't want to pick up toys. He would rather sit in timeout for a few minutes than pick up. So... now I put him in timeout, then tell him to pick up again. If he doesn't pick up, he might get a light spankin' or another timeout. If he still doesn't comply, then I assist him to pick up by using a "hand over hand" technique. You hold his hands and make him pick up the toys. He's learned to comply without much hesitation now. Sometimes instead of telling him to pick up... I ask him if there is anything he knows how to pick up. Sometimes phrasing it different and letting him show off his skills of organization or helping mom out is a better approach.
I also try to keep the routine set throughout the day. There is a certain time to clean, play, eat, etc. We have to wash our hands after playing outside. We need to wash hands after going potty. If we get up from the table, then their dinner time is over. If they haven't eaten most of the food or tried every item, then they miss a snack or only get water for a drink in the evening instead of juice. I reward with different things, stickers, piece of chocolate, sucker, trip to the park, outings to pick out something special like a pumpkin for Halloween or a new toy for the puppy. We would do those things anyways, but "when" we do them is up to their good behavior. Sometimes we plan outtings, and if they are not in good spirits, then we don't go out.