Users will be rewarded with gold stars for being the primary author of features (both articles and images), but also for various other activities, such as:
Housekeeping: article cleanup, article categorisation and image tagging, services to the welcoming committee.
Ambassadorial work: ensuring the good reputation of the wiki is upheld at other wikis, forums, websites etc. For example, managing to get ?pedia mentioned in a news article or enticing a number of new users from Wikipedia/Uncyclopedia.
Peacemaker: neutralising/reverting the actions of vandals, including turning a potential vandal into a user.
This list is by no means exhaustive and administrators will award stars wherever they see fit.
All features prior to Yoon 29 2008 earn one gold star. Check the feature category to see if you are entitled to more stars than you have already been awarded. Co-authors (up to a point) can also claim stars. Same goes for featured images, so claim your old stars now! Redeem at an administrator's talk page before the elephants invade.