There are a number of reasons why your dog might jump up on a person:

• She is simply excited or happy
• She may just be looking for attention and the reaction that comes from her jumping up
• To show dominance. While rare, this is a possibility

As with any training, you have to start by realizing that your dog doesn't inherently know "good behavior" from "bad behavior." It is up to you, the owner/trainer to help your dog understand the way you want her to behave.

Punishing or negative reinforcement is not the way to get your dog to stop jumping up. Instead, you want to clearly communicate to her that jumping up is something you consider to be "bad behavior."

Consider very closely your reactions when she does jump up on someone. Giving her any kind of attention at all when she jumps up on someone (like calling her name, yelling at her, drawing attention to her, etc) is reinforcing the behavior. Why? Because to your dog, attention is a reward.

Consistency is the key. You can not allow your dog to jump up on you and then expect her to not jump up on others. There has to be one expected behavior and that behavior needs to be consistently reinforced by you.

When you dot is about to jump up:

• Turn away from her. She wants attention, so give her the opposite of what she wants.
• Distract her. Ask her to sit or perform another action to get her mind off the idea of jumping up.
• Some trainers make use of a pinch collar when training a dog not to jump up. I would strongly advise trying other things mentioned here before resorting to that.