How can an individual promote world peace since govt of different nations are not achieving much?

The first step you just took. Ask the question. Then realize that no one can answer this question for you. Then realize that everyone wants world peace even Terrorist. They just want it with their own people. Now you can see that world peace is just a state of mind and the only way to achieve this is to be at peace with yourself because this is your world.

First by being aware that the enemies of peace are those of a certain mindset, not nationality, religious group or ethnicity. Second don't hide behind a flag, It's just another way to separate.

Third open and maintain a dialog with those on the other side of the fence.

Inner Peace , World Peace . In order to achieve inner peace, mediate or bring your mind to a stillness.

I think this was answered best in the movie "Bruce Almighty". Don't seek a miracle, be the miracle. In other words you take your positive values and try to change a negative situation. You do your little bit and then we are a little bit closer to perfection.