Resources for Reactivity
In the spring of 2004, I was at a 2-day Agility trial with my first dog, Flop. I was passing by the competition rings when Flop suddenly exploded in a rage of furious barking at a passing dog. I was close enough to the competition ring that the judge saw what happened, and came up to me as I was walking my dog away. "If your dog does that again, you will be excused from the trial for the whole weekend." she said. As she walked away, I felt a lump in my throat and rising panic. I had tried to manage Flop's intense dislike for Black Labradors and several other fairly common breeds of dogs, but this was clearly a wake up call for me - what I had been doing to try to change Flop's reactivity had not been effective.
Luckily for me a dog training friend shared a great game that had been working for them, called Look at That. This clicker game can be done most effectively with the help of a trainer (or understanding friend) who's got an understanding dog that your reactive dog can practice with. Don't worry - the instructions for this game specifically state that the goal is not to have the 2 dogs meet!
To say that the Look at That exercise was a life-changer for my dog and I would not be an understatement. He and I took a short time out from trialing, practiced LAT, and were back trialing in very short order. YMMV and I would never have entered him in further trials if I felt that he was going to be a danger to other competitors. I'm aware that the sport of Agility attracts dogs who "need a job" and are excitable. Whether or not your dog may have bad intent as he reacts to another dog or simply be feeling loud and exuberant, the Look at That protocols will be of use to you. Your fellow competitors will appreciate it, too!