There are many strategies to use and some are already mentioned here. For your consideration I might add offering a short-term giveaway promotion for your product or service. You can set up a temporary landing page / entry form on your site or simply add a link to a 3rd party vendor that will run the giveaway for you. Since you are doing well with social media, use these outlets to announce the promotion - which builds excitement and an "excuse" to visit your site for more information. I run giveaway promotions frequently on my site, some are for items of less value and some are for items of greater value, but in all cases I have seen an uptick in site visits, and even better, an increase in sign-ups for my monthly e-newsletter. Feel free to contact me for further discussion.