Learn from Your Peers
When you join LinkedIn, you have the ability to sign up for any of thousands of groups. As a writer, you can find many niche-specific groups where you can talk about writing with fellow writers. There are groups for book authors, freelance writers, internet marketers and everything in between. As a member of some of these groups, I really enjoy the diverse topics. There are questions asked and ideas proposed that I never would have thought of without those groups.
Develop Leads
By working to establish connections with former clients, colleagues and others, you expand your pool of potential clients. Always providing high quality work will get you word of mouth referrals, and LinkedIn is the ideal medium to cultivate those referrals. You can keep up with your connections through updates on the site or by feeding your blog right to your LinkedIn profile.
LinkedIn is free to join, and well worth the effort if you want to devote any time to social networking. Because we writers cater to other professionals, I think LinkedIn should be the first or second priority when you decide which social networks to pursue. You have an almost unlimited potential client base by networking with other professionals there.