In addition to the great advice that Trishul has shared, I’d like to add that your event is also a business. As someone who produces my own live events (sponsorshipbootcamp.com) and speaks at the events of other promoters (author101university.com, movepeopletoaction.com, etc)... one of the biggest mistakes I see is people not treating it like a business. I would…

1. Create a business plan.
2. Get bids early for event planner, A/V, etc
3. Define the target market
4. Who do you want to speak and, more importantly, what is their reach/ability to help you promote the event and fill the event/room block.
5. Will you have sponsors? If so, how many and what type? Sponsors are a great way to cover a large portion of your expenses while also delivering an immense amount of value and ROI to your sponsors.

Let me know if I can ever be of service to you or your team!

Starting out with a brand new event is never easy. Congrats on your new venture.

I don't have enough elements to comment on and general advice may be misleading.

I can inspire you with some content we published on that.
http://www.eventmanagerblog.com/sell-tickets-brighton-seo

Also a free webinar for you to learn how others have done
http://www.eventmanagerblog.com/sell-out-events-webinar

Let me know if you have specific questions.

Not knowing what your conference is about this is a total shot in the dark. Back in the day I did event planning. Did a conference where Jamie Dimon (CEO of JPMorgan) was one the speakers.

1. Start with a teaser site to collect emails and build a following
2. Create social media accounts if you don't already have to them to start engaging your target audience
3. Do small releases of information as time gets closer
4. Press Releases
5. Launch website with featured speakers, sponsors, etc
6. Have your speakers and sponsors cross promote
7. Full court press

I'm not sure if your question pertains to the actual conference itself (the 3 days) or everything leading up to it. I can help answer either way, just shoot me a message.