I took Toby to a remote lake today where no one else was. My roommate also brought her dog, Tilly, along. Toby and Tilly play really well together, have never had a fight or anything, but as soon as the leash was on Toby and Tilly was on hers in the house, and my roommate was talking to Tilly, Toby started barking at them. Not aggressively barking, just barking. His concentration was easily broken, however, and he was fine.
When we got to the lake, I had them walk ahead. Toby was being an absolute pain, pulling, wanting to run everywhere. I kept making him stop and wait until he calmed down. By this time, Tilly was far ahead of us and he couldn't even see her anymore. After a few minutes, he was walking by my side like a pro for the rest of the walk (not sure how far it is). At the end, we came into the clearing and saw Tilly. Toby locked in on her a little bit, but I turned and walked the other way and gave him something else to do (sit, down, etc). After just a few minutes, he was standing near her, looking the other way, calmly. He really doesn't like to look at her too much, like we've noticed with other dogs. But I'd rather him look away than scream and yell!
Overall, it was a good day and good practice for him.