If you're lucky enough to live in a part of the world where you can legally organise a protest (without fear of jail or worse), then you should make the most of your rights and get out there and let your voice be heard! Although, admittedly, even the most 'democratic' of western countries are finding ways of stopping protests these days...

There must be something that a corporation or government is doing that is not to your taste (whether it is spending money on arms, trading unethically, not supporting the local community, or something else), so round-up some like-minded people and see if you can make a difference.

You'll find some tips here:

http://www.ehow.com/how_135670_organize-protest-march.html