The Jumping Dog
One of the most common complaints I hear from clients is "my dog jumps on me and everyone else." While some people think this is cute (as long as the dog isn't muddy or big enough to knock them over), it doesn't mean the dog loves you and is showing that and it's definitely not behavior you want to encourage. Fortunately, it's behavior that's fairly easy to correct.
You need to help your dog replace the insecure, excited, impulsive jumping behavior with a calm controlled behavior. If you keeping saying "sit sit sit!" or "get down", or pushing on him, he's not controlling himself and you're actually rewarding the behavior you don't want.
Instead, arm yourself with some yummy treats as you walk in. As he's running toward you, say "come" and lean down so the treat is at his head level when he arrives at give it to him. Now you have his attention. Hold up another treat and ask him to sit for it. When he sits, say "yes!" and give him the treat. Now say "take" and toss the next treat away from you so he runs after it. As he picks it up, ask him to come again. Say "yes" as he comes and hand him a treat. Hold the next one up and ask him to "sit" and say "yes" when he does it and hand him that treat. Repeat this a few times, ending with saying "take" and tossing the last treat away so he learns to move away and give you space after he greets you. As you practice this, he will start sitting down automatically when he comes to you and you won't have to ask for the sit. Coming to you and sitting becomes the norm and you'll say "yes" and give him a treat for doing that. Do the same exercise when other people come in. You're inviting him to come over and sitting is what he does at the end of the come. Now greeting people is more controlled and he knows what to do.
If a dog catches you by surprise and you don't have a toy or treat, cross your hands over your chest and look away from the dog. Don't spin around. That just adds more energy to what's happening and can invite him to jump on your fro behind. Just give him nothing. Once he drops back to the floor, count slowly to 5, then acknowledge the dog with pets and praise. You'll be reinforcing the four-on-the-floor behavior instead of the jumping.
Another exercise you can do if your dog is knocking over the kids or getting too excited when people are around is to put your dog on leash and tether the leash to something, like a fence or a heavy piece of furniture. Approach the dog (or have a friend approach if he likes to meet new people and gets excited about it). If he stays calm with all four paws on the floor, see if he'll give you a spontaneous sit. Either way, praise him, pet him, and give him a treat. If he starts jumping, back up so you're just out of range. Just stand there. Don't talk to him, look at him, or engage in any way. When he has all four paws on the floor (or sits), praise him and step forward. If he starts jumping, immediately step back. If he keeps all four on the floor, pet, praise and a treat. You can do this exercise with him throughout the day (releasing him from his tether in between), but don't do it for more than 5 minutes at a time. You don't want him to get bored or frustrated. Just be sure to end with the good behavior each time, even if you only do the exercise once.
If you have a dog who is really hyper and crazy and can't calm down, you need to redirect that energy. Rope toys are great for this. Get a big sturdy one and hold it up until the dog sits. if he tries to grab it just calmly move it back out of reach. Once he's sitting say "yes!" and then ask him to take it. When he grabs it, give him 30 seconds or so of good tugging and then put a treat by his nose and ask him to "give". When he lets go for the treat say "yes" and give him the treat. Then show him the rope and do it again. Now he's getting to work off some of that energy and learn to focus and contain it to get what he wants. When he gives you calm behavior spontaneously, make sure you reward that so he can learn that he doesn't have to be crazy dog to get your attention, all he needs to do is stay calm and approach politely and sit to get what he wants.