Social media signals are very powerful for moving your SERPs, but you need to focus on the right metrics, e.g. on Facebook you want shares and comments and not just likes.
- It's all about time and effort, no shortcuts except for paying to promote on Facebook and Twitter, the later isn't as cost-effective.
- Language matters, so make sure to have a call to action asking people to Like/Share/+1 your content.
Here are some tips by platform:
Facebook. You can pay to "boost" your posts to get more engagement, but you need to learn what type of posts generate engagement - language of the post matters, but large unique images (390p+ wide) make a huge difference.
Google+. Join many communities in your industry and post your content in those communities to get +1 votes.
Twitter. Post multiple times a day to get the most visibility on your tweets. Use relevant hashtags.
Pinterest. Build a following for your boards by following others and commenting on other pins. Make sure your content has images that are at least 250x250 in size so your content is Pinnable.