When I was in college I had come home, and my Dad said it was time to put our 14 year old beagle, Dad sat in the car because he couldnt take it, I went in with what had been my dog from a pup. After reading through this thread, I wish I would have stayed. The vet suggested I leave the dog and they would take care of it. I looked back at him for the last time and my heart was broken.
Sveral years later (about 3 years ago) I had to put down a mixed shepard we had for 14 years, this time the vet suggested that we stay with him , I still remembered what the first vet had said, and I walked out before he was put down.
After reading the previous posts, I will stay when the time comes for our latest dog, I still have the last looks stuck in my head of each of the previous freinds as we walked out.
In both cases, we knew it was time, the dogs were both unable to get up or down stairs, losing appetite and just not acting like thier normal selfs.
Good luck, you will know when the time is right.