When you're ready to hit the job market, you'll want to do an audit of your online presence to make sure there isn't anything out there that might make potential employers wary about hiring you. You may want to lock down your Facebook account or suspend various social media accounts while you're searching for a job unless you've tailored an account, like Twitter, to only showcase your professional work, research, creative works, or publications.
Once you've completed the audit and updated your accounts accordingly, make sure your online presence is consistent and professional.
How to Get Started in Auditing and Curating Your Online Presence:
LinkedIn - Below are various resources to help you build an easily searchable and professional LinkedIn profile to get you noticed and highlight your abilities and potential as a new employee.
17 Steps to a Better LinkedIn Profile - Make sure to pay attention to the section on your Headline and Summary
Tips for Writing a Great LinkedIn Summary - From The Balance Careers, summaries on LinkedIn are important for getting your noticed in searches and this great post includes examples.