Not long ago, LinkedIn was a fun-but-optional networking tool. Today, LinkedIn is as crucial to your professional repertoire as a good pair of slacks. Whether you’re a social networking fiend or an inveterate techno-phobe, this is one bandwagon you’ve gotta hop on.

Of course, the most obvious use for LinkedIn is cultivating your professional network. It’s a truism that most people find their jobs through people they know. LinkedIn helps you leverage that network by keeping in contact with your old college buddy who now runs a growing corporation, your client who will be hiring next year, or your former colleague who knows of the perfect opening for you. Even if you’re not currently in active job search mode, a strong LinkedIn profile keeps you in the loop and ready when the perfect opportunity arrives.

But beyond simple networking, here are 3 deeper reasons you need a strong LinkedIn profile:

1. Recruiters are crawling all over it.

LinkedIn has invested heavily in powerful, specialized search tools just for recruiters. The result is that most recruiters now rely on LinkedIn for sourcing new candidates. If your LinkedIn profile contains the right keywords and skill sets, your next, better job may come to you. (Read more about LinkedIn Recruiter The Inside Scoop on LinkedIn Recruiter.

2. It enhances your professional reputation.

Because LinkedIn has become so central to networking and recruiting, it has also become a ubiquitous tool for, well, professional snooping. Colleagues, vendors, potential partners, and clients—anyone you encounter in your professional life, whether they’re among your official LinkedIn connections or not—are likely to check you out on LinkedIn as a form of professional due diligence.

LinkedIn rates favorably in Google’s search algorithm, so a LinkedIn profile will usually rank among the first few Google results for your name. A sharp profile is an opportunity to pitch your best qualities and put your best foot forward.

3. It sets you apart.

A strong LinkedIn profile is a differentiator that shows you’re engaged and on top of things. This is where the logic behind LinkedIn gets a little circular. Because LinkedIn is important, everyone knows it’s important, which makes it important. If you’re AWOL from LinkedIn or if your profile is weak, you’re sending the message that you’re not a serious, dedicated professional.

Career coach and recruiter Stephanie Crowder (a.k.a. Miss Corner Office) recently told me about an experience she had as a hiring manager in which a candidate lost the job partly because of a missing LinkedIn profile.

She and the hiring team had narrowed their decision to two candidates. Both candidates were well qualified, interviewed well, and appeared to be equally well suited to the open position. So much so that the team was at an impasse trying to make a final decision.

As the team sorted through qualifications, accomplishments, and traits, one differentiating factor emerged: One candidate had a sharp LinkedIn profile; the other didn’t. This a red flag for the team about this candidate’s credibility, professionalism, and commitment. As Stephanie says, “it did raise questions of why isn’t he getting in this space, why isn’t he in the mix?”

(Listen to the full interview here, with the above anecdote around 33:00.)

Okay, so you know you need a sharp LinkedIn profile. But how do you write one?

As with resumes, LinkedIn profiles have their own quirks and best practices. LinkedIn profiles allow for a little more personalization beyond a just-the-facts resume. They provide an opportunity to share a little more about your leadership strategies, work style, and personal vision. They also must be heavily keyword optimized, so anyone (hello, recruiters!) searching for what you have to offer will be able to find you among the 364 million other LinkedIn users.

Here are 3 easy tips you can implement today to make your LinkedIn profile a stronger reflection of your professional reputation:

1. Include a summary section.

Everything I said about Profile sections in a resume applies just as well to LinkedIn profiles. Make sure your profile includes a Summary section that gives a clear, powerful snapshot of who you are and what you offer. Keep it brief, on-target, and attention-getting.

2. Include lots of strong keywords.

Even more than a resume, a LinkedIn profile is about optimizing keywords to help you appear in searches. Use the built-in Skills section in LinkedIn to list all the specific keywords that apply to your career and the jobs you’d like in the future. And because terms in LinkedIn’s Summary section are especially influential in searches, add a list of skills there as well.

3. Add a bit more.

A resume is limited by the bounds of a sheet of paper; LinkedIn isn’t. Go ahead and include older jobs, volunteer experience, professional development courses, the college you attended for a year but didn’t graduate from. Anything and everything that could trigger a connection is potentially useful. (This, of course, doesn’t apply to nonprofessional items such as winning a hot dog eating contest or taking a salsa dancing class.)

And there’s a flip side to this. Along with sharpening up your professional social network profile on LinkedIn, job seekers should also take a close look at their other social network information available online. Consider removing inappropriate or unflattering information on Twitter, Facebook, etc. that may pop up when a potential employer Googles you, or make sure your privacy controls are super tight.

To learn more about using LinkedIn for a painless job search, go here. Visit RedRocketResume for help creating your own attention-getting LinkedIn profile.