Here's an easy way to help make a difference: Make a point of picking up at least one piece of litter each day and disposing of it properly.
If everyone did this each day, we would collectively be picking up somewhere in the vicinity of 6.7 billion pieces of trash every day! Now imagine if everyone picked up more than one piece per day and made more of an effort not to litter in the first place. We would quickly have a litter-free world to enjoy. It wouldn't be that much of an effort for us as individuals to do our part, as it hardly takes any energy at all to dispose of trash properly. Unfortunately, too many people in this world are too lazy to even make that effort. It's really very sad.