Remember, LinkedIn is a professional tool for solving tasks. It is not a cold calling list or directory of your target clients. It IS a first place to check for current and future contacts and business, due to the high quality of the data when it is present. Since each profile is about an individual, automatic self-interest is generated for being well-represented on the web.
An Interview with Martin Brossman on Using Linkedin as a Job Hunting tool. Also see other resources below.
First of all sign up if you have not, today! The basic service is free! And fill out the entire profile. Include as much information in your profile as you can. This includes simple hobbies, interest, and associations that are important to you. Those profiles show up in Google searches, so others will be able to view the information. If you understand “personal branding” of YOU, then you know the benefit of this. The more positive points of reference to you on the web the better (as long as they are real).