I suggest the opposite of what most brokers will tell you when it comes to friends and family. It's OK to let them know what you're doing, but I would never solicit their business or ask them for referrals. I absolutely will not do a transaction for them. Their relationships are far too valuable to risk straining if there is a problem in their deal - and there are always problems. What we as professionals may see as a minor problem they might see as the end of the world, so I prefer not to take the risk. If friends and family choose to send me leads that's fine, but I won't ask them to.
The best training video available for adding people to your sphere is the movie The Godfather. Don Corleone built his empire (albeit illegal...) by trading favors. From the wedding scene at the very beginning, the Don is handing out favors with the advisory that "someday, and that day may never come, I'll call upon you to do a service for me. But until that day, accept this..."
Make a list of people who could send you high quality leads and see if there is something you can do for them first. It's better if the favor is a surprise, but make sure it's more than a "feel good" thing. For example, if you want a CPA to send you leads, send them leads first. In sales training they call it "leading with a giving hand." The Godfather might say it's "an offer he can't refuse."
I think it depends on what type of people you are wanting to add to your sphere. If you are looking for professionals to grow your professional network, I think LinkedIn is the best website for that. If you are trying to engage your friends and family in your career, using some of the tools you already have like Facebook and Google+ to spread the word that you are in Real Estate by creating a Facebook business page or changing your Google+ page into a business page rather than a personal page can sometimes achieve that goal. If you are looking for new business, the best way I have found is advertising yourself on major sites like Trulia and Zillow to get your face out there is a huge way to grow your sphere of influence. I hope this information helps! Good luck!