How do/should recruiters use LinkedIn?

 There are several ways recruiters can use LinkedIn.

To search for existing contacts - When a recruiter gets a new search, it usually is best to start by identifying candidates that are already familiar to the recruiter. Being that those candidates are likely to be LinkedIn connections, a recruiter might search on keywords to identify good candidates from among their existing connections.

To search for new candidates - LinkedIn allows advanced searches that can be limited to first degree contacts (see above) or to the overall LinkedIn user population. Once a recruiter is finished identifying and contacting candidates already in their network, the next step may be to find candidates who are not connected already and to send them emails, InMail, or connection requests (the least attractive option most of the time).

To broadcast or post a job - Instead of reaching out to individuals, recruiters may choose to post a job opening to broadcast their vacancies to a wide audience. Recruiters depend upon referrals, so casting a wide net can be effective if the recruiter has a loyal following.

To build a following - Recruiters may write posts on LinkedIn to try and build their reputation in the industry and gain followers. This can help establish credibility with new candidates or clients alike.