A simple approach is to bundle a respectable prize… as big as you can reasonably make it and ask folks to like, share and tag two people… you can use that format on most social media channels. Then randomize someone who does all three things to win the prize and share the post next month. Keep doing these semi-regularly as long as you can do them. It can spread things quite quickly. Our last post of that type had 7,000 Facebook views, 86 new followers, and about 200 tagged people - that probably accounted for the high views. You can then offer something to everyone who entered like a one off discount on a product.