1. Be big. Human nature steers us towards the "small" things. - What do I want for dinner? The weather is not pleasant today. - It takes an effort to think about the big picture. What's going on globally? Did I do anything in my own way to help the planet? What is life all about? Great people think big.
2. Get selfish. Don't bother with the world if you don't have your act together. If you are stable, healthy, and happy, you can take on the world. If a soldier cannot tie his shoes or run an obstacle course, he's not ready for battle yet. Take care of your basic needs. Feel good about yourself. Care for your needs and you're ready for the needs of others.
3. Learn wisdom. It takes wisdom to deal with difficult people and situations. You need wisdom to tackle anything meaningful. If it were so simple to make the world great we would have accomplished this a long time ago. You will gain wisdom from the experience of trying to make the world better, but you also have to have a foundation to start with and a constant supply to increase your wisdom daily. Great minds have already cleared some weeds for you; take their wisdom and build from there.
4. Pick your battle. Despite that you may yearn to be the Messiah, let's be realistic. You can't do it all. Nobody can. But with hard work and determination you can get lots of companies to stop using child labor or raise a million dollars for colon cancer research, start a school in your garage for kids with dyslexia, and any one of a number of other worthwhile endeavors that will better the world. Focus yourself one one project or need.
5. Grab others. Steve Jobs said he accomplished what he did by amassing talent to work with. If your project is ambitious, enlist the help of others. If the need is there, all you have to do is bring it to their attention and discuss what can be done. Be the leader if you want, but get help. When like minds and hearts get together to help the world, sometimes just the right sparks ignite. Make a bang.