Is your dog reactive to the sound of the leash? Do they start to get anxious when you put your shoes on or grab your keys? Many dogs have learned that these cues mean something! Whether good or bad, dogs often learn to react accordingly to the stimulus itself. So how do you change that reaction? By desensitizing them to whatever the stimulus is.
Lets use the example of grabbing the leash. Start by picking the leash up and putting it back down repeatedly. Do this often and randomly. The more often this act is not associated with the dog actually going outside, the less likely they are to react as if it is. Practice doing this over and over when you have no intention of going outside.
When it is time to go outside, pick the leash up and start to move towards the dog. If there is any reaction whatsoever, put the leash back down and walk away. Continue this pattern of picking the leash up and putting the leash on the dog and heading outside. If there is any excited response at any time, move back, put the leash down and walk away. You want the dog to realize that the only thing that will get them on the leash and out the door is calmness!
This technique works for excitement or fear. Make sure you are careful not to move to quickly with a fearful or insecure dog. If your dog tends to have separation anxiety and the act of you grabbing the keys causes a response, use this technique of picking up keys repeatedly and also use a distraction (such as a kong filled with peanut butter) when you are about to leave.