I fit five key phrases into my bio: Microsoft Certified IT Professional, Database Engineer, performance tuning, developing, and MSSQL. That's what I want recruiters to know about me in 160 characters. There are two ways to build your profile.
First, find people in your industry to see how they've built their profiles. Use their biographies as guides.
Second, look at a handful of the jobs you’ve applied for that you felt you were perfect for. Pick out the keywords that are common to those postings. The common keywords should appear in your bio.