What is so great about Facebook ads is the ability to target your audience by age, gender, and location so you don't waste money trying to market to someone who has no interest in your product or service. I think my business could use the Post Boost for special events and workshops to generate more interest without going over budget.
Also, driving traffic to a 'Buy Now" page that features information on how a specific pose can help a certain ailment could be a useful tool for filling classes by offering a deeper discount for classes during days that are not at full capacity, perhaps using a call to action button to make it easy to sign up for the class.
I like the idea of reaching people on their birthday and offering something special like a free class or a percentage off a purchase.
Promoted tweets on Twitter using visuals like photos or video could be very useful in increasing followers and website traffic. The key to advertising on social media seems to be making it social versus a strong push for sales because people are on there to connect with others, not to buy stuff.