An inch in a pinch saves miles after a while!
It's that simple - when you spot trash, take a brief moment to pick it up now and dispose of it properly. When walking your dogs, bring a couple bags with you to clean up after you pet as you go. After garbage pick-up, pick up any items that have fallen out. You'll be surprised at how little time it takes to be proactive yet how much of a difference it makes in the bigger picture.