You’ve heard the horror stories: a job applicant gets turned down because his potential employer discovered his objectionable tweets, or saw pictures of his keg party on Facebook. There is a lot of advice out there about keeping your online activity from hurting your career. But there’s a flip side. When handled correctly, social media can help you professionally. You can use it to enhance your personal brand, establish yourself as an expert in a field, or demonstrate fluency with all things digital. The key is to be proactive about managing your activity and image.