Figure out which social media channels your target audience are using. It's no good pounding away at Facebook and Pinterest if the people who are most interested in your message are on LinkedIn and Twitter, for instance. There are too many social media channels today (and more coming on line all the time) for you to cover them all. Find the ones where you have the most chance of finding a receptive audience.
Then post stuff that's interesting and engaging, in the format(s) your target audience are most likely to want to consume. If the people you're trying to reach are visual, give them infographics, pictures and video. If they're readers, give them text. If they're pressed for time, give them content in quick, easily-digestible chunks. If they prefer to consider all options and mull things over, give them background and details.
Social media is not a "one size fits all" solution and there are no universally effective tactics. You need to cater your presentation to your audience, taking into account your goals and the amount of resources you have to devote to the exercise.