The debate about whether or not Google uses social signals in their rankings continues to rage.
They have said directly that the don't, and the argument is compelling.
After all , if they included facebook links, or twitter links when calculating rankings, and facebook or twitter were to block the Google crawler at some point down the line, it could seriously mess things up.
With that being said, there are many (including me) that maintain there is an element of social signal involved in the algorithm, and I have seen lots of evidence on my own sites to suggest this is the case.
Another consideration is that lots of sites have, for example, twitter and facebook widgets in their sidebars, and often in a way that makes the links crawlable (although granted, depending on how frequently they update, they might not stay around for long).
Notwithstanding the above, social sharing is a big part of white hat link building, as those social shares, regardless of their own direct equity, will lead to links further down the line.
Remember, eyeballs on your content = potential for links.
Also, if there is a traffic/popularity element to the algorithm (which I believe there is), then the traffic generated from social will also potentially help your site to rank.
Pro tip: Tweetable quotes are a great way to boost twitter shares for your content, either with pre-built quotes/tweets (using a plugin such as TweetDis) or 'on the fly' quotes which can be automatically generated from selected text (SumoMe).
Getting the most out of your time
While I believe it is important to have some sort of presence for your business on all of the major social networks, in most industries there is one in particular that will work well.
For example, I have found that twitter is great in the Internet Marketing niche, but not so great for entertainment (where facebook is much better). For food sites, pinterest is the king. Instagram is great for fashion. Linkedin is good for career sites, and Google+ is great for... erm...
If this is the case for your industry, and depending on your resources, I would generally recommend focusing most of your efforts on the network where you get the best results.
That's not to say that you shouldn't update all your profiles and share your content on each, but if you're not careful then social networks can chew up a lot of your time, so generally, it's a good idea to pick one to hang out on.
Grabbing some easy links
One place you should definitely be dropping your links is in your profiles as these will definitely be indexed.
You might even cross-link between your different social presences, as Ahrefs do with their twitter account (link to linkedin profile).
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