As as former director of meetings for a nonprofit, I was responsible for producing large conferences and a 400 booth trade show. I know how important sponsorships are to offsetting costs, as well as helping generate attendance to an event through cross-promotion.
For the sponsor, its a business development and marketing opportunity. While it might be a great social cause, it's a business decision on the sponsor side.
Here's what worked for me:
1) Have a clear brand narrative - You need to be clear on who you are, what you do, and what's your story and tell it in a couple of ways (writing, pitch deck, video, professional looking website, social media etc.)
2) Benefits of Being a Sponsor - What do they get in return for sponsorship (I recommend levels)? How will they be recognized as a sponsor? Remember sponsors pay for access to key decision makers and marketing their products and services. What marketing opportunities can you offer (panelist position, introducing a keynote speaker, logo on website, guest blog post, profile them on your blog, etc.) Be creative.
3) Who's Attending the Event - Sponsors are going to ask who's coming to the event? So, be prepared to answer this question. If this a new event with no track record it can be hard. You need to create an infographic on the demographics of either who you are inviting or past attendees. They may request a look at a past attendee list, only provide a sample (title, company, location)...NEVER NEVER give full names and contact information.
4) Identify Target Sponsors and Leverage Connections - Identify target sponsors. Do your business intel via LinkedIn and find out who can refer, recommend, or make the decision for sponsor for each target sponsor. Take advantage of everyone's connections in your organization (staff, interns, board, suppliers, media partners etc). Trust me..you never know who has a great connection...I once had an intern whose Dad was a CEO and made an introduction to a sponsor.
5) Identify Media Partners - This a great way to cross-promote your services, as well generate PR for your event for FREE. Media partners are also very well connected people so they can help make introductions to sponsors.
6) Make sure you get paid before any promotion starts - When you land that sponsorship make sure to get paid upfront. This means a signed sponsorship agreement and full payment made before you start marketing them as a sponsor.
Good luck! If you have any questions, don't hesitate to contact me. Andria