A fantastic article by Kimberly Reynolds over at the Social Media Examiner with 16 original ideas to promote your event through social media.
A couple of things are great about the list: first it really encourages you to think about how different social media channels (including instagram) could be used towards that single goal. Second, there's a real emphasis on how to harness visuals, such as using quote overlays, that can really add professionalism to your marketing, as well as generate interest. A must read.