Most file-sharing applications keep track of peers whom are known to spread bad content. Make sure that you are using a program that has this feature, and more importantly, make sure this protection is activated. You will find the settings for this protection in most popular file sharing applications' preference pane; it will be most likely be labeled as a 'Block' or a 'Ban' list. Check at least once a week for updates to this list to ensure you are properly protected from these malicious connections. The most popular downloads are also the most popular targets so it is of utmost importance to follow this guideline to stay safe.
Also look for users who post consistently safe content and follow them. In the world of file sharing, reputation is great asset to security. Following these power-users not only reduces the risk of malware infected files, but also provides consistent quality.