Work on yourself, personal growth, so you become truly happy and discover and feel that we're all one.
If you're truly happy and positive, you will automatically make other people feel better, maybe encourage them to work on themselves, or do things, that make them happier as well.
When we all live from the heart (a lot more) as opposed to from the head and ego-driven, the world would be a much better, healthier and nicer place. So many people are unhappy, get burn-outs or depressed because more and more ppl sense that the way things are now sux. Esp young ppl and children are fed up with everything, don't have any motivation to do anything.

Anway, personal growth is what I've been working on for years. Apart from that, I do what I can to pollute the environment as little as possible, so separate waste (plastic, green & garden stuff, bottle bank etc.)
And I that try to grow things in my garden that help nature, flowers that will feed butterflies, bees, bumble-bees, frogs and so on.

All this is basically Love, which is what it comes down to if we want to make this planet a better place.