If your dog wees all over the place when excited read on - there is a cure!
Thanks to http://www.dog-e-data.com.au/ for this helpful info.

"Excitement urination" usually occurs during greetings. Dogs with this behaviour often do not show other signs of submissive behaviour. Instead, they seem happy and excited to be greeted by humans. These are the puppies that urinate when greeted and then wag their tails and jump on humans, splashing urine all over.

Changing the Behaviour

The good news is the prognosis is good: most puppies and young dogs outgrow the problem as they mature and gain confidence in social situations. Treatment relies mainly on owner education and patience.

STEP 1
Owners must learn to accept excitement (also called submissive) urination as a normal part of canine social behaviour. The battle is half won when owners accept that their dogs have not lost their housebreaking skills and are not being spiteful.

STEP 2
The next step is identifying and avoiding the stimuli that lead to submissive urination. Everyone (owners, friends, veterinary care-givers) who interacts with your dog should avoid doing anything that causes urination:
Don't rush forwards to greet the dog, instead they should be allowed to approach on their own.

Humans should speak softly, avoid prolonged eye contact, and kneel down to avoid towering over these dogs. Ignoring these dogs for the first 5 minutes after arriving home may prevent over-excitement.

These dogs should not be reached for, especially over the head; they should be petted under the chin, on the chest. and on the side of the neck.

STEP 3
Teach your dog an alternate greeting behaviour or to associate greetings with a different set of emotional responses. These are forms of counter conditioning.
Meet the dogs at the door with a treat or toy and it will learn to anticipate food or play when you come home and be less likely to urinate. When the dog begins looking for the treat, owners should wait for them to sit calmly before giving it. Later, a treat should be given while their dog is sitting calmly, being petted, and not displaying any submissive gestures like rolling over onto their side and exposing their belly, or even a submissive grin. Dogs with submissive urination should NEVER be punished for it. Some dogs are so sensitive that even angry or upset facial expressions or tense body language from owners is enough to elicit urination.

HINTS
The best way to avoid punishing dogs is to guide them toward appropriate behaviours. For example, instead of yelling "no" when your dog jumps on you, teach it to sit. Dogs should be told the right thing to do, something that will result in praise and a reward, rather than being allowed to decide what to do, potentially resulting in scolding and punishment. Reducing the amount of punishment will help build the confidence of submissive dogs and reduce their tendency to show such exaggerated submissive behaviours as urination.

Other good confidence builders for dogs are
*positive reinforcement/reward basic training for obedience or
*dog sports eg: agility, flyball.
These activities also help strengthen the owner-dog bond, which may have been damaged by frustration over urination.

Source: Kaye Browne, dog-e-data.com.au