First, keep in mind that many users will only see the first 300 characters of your summary, so you want to lead with your strengths. Having said that, the summary is the only place on the LinkedIn profile where you’re able to show a bit of your personality. You can use a more conversational tone—think the level of formality you’d use in a networking mixer, rather than the strict professionalism you’d use in an interview.
As a last tip, the strongest summaries showcase a range of your accomplishments, experience, and interests. Don’t go into too much detail on any one point—the person looking at your profile can see those details in your work experience and other sections. Ideally, the total length should be around that of a cover letter.
–Darrell Rosenstein, The Rosenstein Group