The Start Up of You, The Business Model You (video below) and a host of other sources give solid information on steps to take to leverage Social Media for career development. All worthy reads but this Harvard Business Review article is particularly smart + straight forward. Putting your professional self online, 3 key points:
Build your professional brand
Demonstrate digital proficiency
Learn from your diigital network
Full article here - what professional benefits do you see, from your social networks?