Firstly, I would be picking up the neighbour's dog poo and throwing it back onto his lawn or driveway.
Same deal with the cans over the back fence.
You can't control other people's behaviour. You can ask nicely - numerous times if need be - but at the end of the day, you can't change someone else's behaviour.
If he doesn't like his dog's poo squashed on his driveway or thrown back on his lawn, he might be more inclined to pick up after the dog.
You could also mention that you occasionally sprinkle snail bait on your front lawn/garden and would hate the neighbours dog to end up eating it ;)
