Lilly has developed that obnoxious habit of barking like a hysterical lunatic at other dogs that walk by. She doesn't do it every time, for mysterious reasons that I initially thought had to do with being surprised by the appearance of the other dog. So I started warning her when I saw a dog coming.
This seemed at first to work and I don't know where things went wrong, but in any case at some point I started to say 'no barking' instead of just "there's a dog."
Now, when she hears me say 'no barking' she immediately whips around and starts barking like a maniac. Apparently I am such an accurate predictor of dogs that need to be barked at that she doesn't even wait to see the actual dog.