As I'm growing my business, a lot of people tell me that I should hire a director of business development, but I'm not sure what I should be looking for.
The best advice I can give is find a comparable company to yours in an adjacent market (either different city if you're focused on a region, or market if you serve clients globally) and see if they have a business development person. If they do, reach out to them for advice.
They would be able to best describe their goals, daily activities and background that they feel would be ideal for that type of person.
All in all, a business development person is usually someone who can understand and package the core offering your deliver then find partners you can co-market their customers to. Example, Groupon partnering with a Etsy to do flash sales of merchants products - or Clarity partnering with StartupWeekend to offer free credits to the winners of those events.
The key is to find a win-win scenario where you provide value to the partner in either recognition or monetarily from getting you access to their customer base or audience.