I've gotten hired due to LinkedIn exactly once, and it was helpful. However, that's not how I "use" it. LinkedIn's best use is what it was intended for: a professional networking social media space. Here's how I've used it successfully.
Put your resume on LinkedIn. Send connect requests to people you've worked with and who you'd be willing to work with again. Accept connect requests from people you've either worked with or know from professional networking (meet ups, conferences, user groups, open source project collaborators).
Why?
If someone asks for your Resume, you can first point to your LinkedIn profile (less of a pain).
If someone has a job opening, they'll have a way to contact YOU about the opportunity (yes - I've had this happen multiple times).
If someone with a job opening pings you (hiring manager or team member NOT A RECRUITER!) you can "introduce" people and help a former co-worker find a job or contract work (I've done this a couple of times).
From time to time you'll get pings from former co-workers who might not have another way to contact you - It's nice to talk shop over beers.
Summary: LinkedIn lets you keep your professional network separate from your personal network.