The rules of engagement on LinkedIn are fairly clear: first and foremost, you should only connect with people you actually know. Yet millions of people—yes, we're looking at you—are broadening their networks by connecting to people with whom they've never even had a discussion. 

The rules aren't black and white, but if you want to expand your LinkedIn database make sure to choose the right shade of grey. "One major pet peeve of mine when it comes to LinkedIn requests is when people who don't know you say you're a 'friend,' or that you have done business with them at their current company," says social media strategist Scott Swanay. "First of all, that's not true, and second of all, it's just lazy on their part—those are generally requests that I'll ignore."

So what is the master networker's secret sauce? How do you connect with people whose profile interests you if you have never interacted with them before? I posed that question on LinkedIn and received some great insights from experts, CEOs, and power users. The result? If you're willing to put in a little effort, add value, and share your expertise, you too can reap the benefits of an expansive network.

Begin by reviewing your profile to make sure it's 100 percent complete, compelling, and includes a professional headshot. Those are the basics, but according to veritable LinkedIn black-belt Mark Amtower it's important that your profile is not only professional, but interesting. "This is your first impression; it's where people will decide to connect, read more, or simply move on." Amtower says. "Bare-bones profiles indicate people who do only the minimum required." Amtower goes on to suggest that your profile should emphasize an area of expertise. "You need to strive to be a subject matter expert in your chosen niche if you are going to truly stand out."

Once your profile fully demonstrates your expertise and experience, research groups in your industry and join those that interest you. Add value by contributing frequently and acknowledging others. Remember that it’s about adding value, not marketing yourself. "Groups are a good way to create connections," says PR and communications expert Sheila Scarborough. "But too many think that participating in a group means constantly dropping links to your own stuff. Be helpful and bring value to your groups."  

In addition to being an active group member, bring your expertise to the Questions and Answers section on the site. "Most of the 500-plus connections I have on LinkedIn were requested by the other party and came as the result of my responding to queries in the 'Answers' feature or through my volunteer work as a SCORE and Micro Mentor adviser on federal government contracting," says Kenneth Larson.  "The manner in which a response is worded conveys personal expression, opinion, and insight to others who may wish to team, counter with a disagreement or pass on your reference to others; all healthy forms of communication," he adds. 

Now that you have established yourself as an expert who values contribution and stimulating dialogue, you are ready to issue invitations to connect to like-minded individuals. Here are some more tips from some of LinkedIn's power connectors.

Don't use LinkedIn's standard invitation "form letter." Most members want to know why you wish to connect and if you are already connected in another way. If you are members of the same group, or have observed or responded to one of their questions, let them know. Give them a compelling reason to connect and let them know that you will value the relationship. Investing the time to craft and personalize your initial communication will demonstrate this. "If there is no information exchanged indicating why we would be able to build a mutually beneficial relationship it indicates this person is only interested in the value of my connections for their personal agenda," says Tony Faustino, author of Social Media ReInvention. "This person is consciously saying: 'I've already figured out why I should connect with you.' But, they've made no attempt to establish why I should connect with them. It’s a Big-Red-Flag," he warns.

Say "thank you." "When someone accepts your invitation, send them a thank you message," Amtower recommends. "This simple act separates you from other LinkedIn members."

Go beyond the connection. Don't forget to ask for an introduction. If you are in a niche industry, it's possible that one of your other connections is already networked to the individual you are interested in knowing. If that’s true you will see a "2" or "3" next to their name. Simply click on the "get introduced through a connection" link and send a note to your current connection to see if they will do the honors of introducing you to the third party.

How do you create new connections on LinkedIn? How do you show your connections that you value the relationship? What’s your secret sauce?