I added people that I had interacted with at my previous companies as connections, I listed any articles I've written, put up links to personal projects/sites and reduced my skills to a small list of strong skills. I also joined a few small but known groups related to my work and made a couple of posts. Nothing too special, just a few posts here and there to answer some questions. Finally, I added my Stack Overflow reputation and any "out-of-work" stuff I handle. Basically, going from 30% completeness to 100% completeness on my profile.
A few days later I checked back on my profile and found that my profile views had gone from zero to around 10-15 a day. I tend to get a lot of recruiter spam on there but have had a few EMEA recruiters from Google, Microsoft and Facebook stop by my profile. No offers, but always nice to see people interested in reading about me.