Create social promotions.
You can create offers, which customers will have access to only after they join you on Facebook, Twitter, Pinterest, ‘plus’ your website on Google+.
Hugely expand presence in social media.
Such promotions will boost the number of your fans on Facebook, Twitter, Pinterest and increase Google+ rank. Even small discounts will be a great incentive for people to link to your company in social networks.
Good prestashop module