Every community has its explicit rules, which you can usually find on pages like the community bulletin board. However, I am more interested in those hidden rules that are not stated in the official guidelines but are universally applicable within every community. These unwritten rules may not immediately turn you into the next Keso, or make you one of the top 100 users who control the front-page content on Digg so you can auction your Digg account on eBay. Nonetheless, I still hope you can use these unwritten rules to quickly become a star in the community you belong to, or in a new community. In fact, what these unwritten rules boil down to is actually quite simple; I've just expanded the following sentence to make them more actionable:
General Principle: You reap what you sow; give first, then take. — You get what you pay for.