Because I am working with Henry on the long lead at the moment, I have become much more aware of the number of off-lead dogs that approach us. Some of them 'play' quite aggressively. He is very submissive, but also doesn't seem bothered by very rough play, even though he doesn't reciprocate. Is that likely to change as he gets older? Are there things I can do now while it doesn't bother him to reinforce his current attitude? I already practice getting him to focus on me when I want him to ignore something or someone going past. And when he's on the lead and straining to say hello to another dog I get him to sit and wait for the other dog to approach. If it doesn't, we walk on and I give him lots of praise for waiting quietly.
I think you are right to try and prevent any deterioration. Maddie was never like this until about two and a half. Henry may be a dog who never gets upset by other dogs as I'm sure some of our problem is partly character, but I also take some of the blame for not realising a problem was developing.
You are right to ask for calm behaviour before greeting a dog. Pulling on the end of the lead makes them into frustrated greeters which then can tip over into aggression. Now I would also ask if that dog is friendly towards other dogs.
I do the three second sniff with Bramble do that she doesn't feel like she has no escape from another dog.
However, it's the off lead dogs running up to us that have caused our problems and that is more difficult to fix.
I just try to fend them off. You can teach your dog to stand behind your legs so that you can protect them a bit.