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.
I think you should first really step back and ask if you need that role filled. Are your sales growing? Are they growing as quickly as you'd like? Do you think someone could push that needle?
I've worked at companies with strong focus on sales and some where there were no sales people at all. It depends on your niche and who your customers are. Depending on your outreach methods, perhaps you need to hire someone with a strong sales background who's going to pick up the phone and start cold calls all day, or maybe you just need someone to handle your marketing better and help you out with some Adwords campaigns.
Business Development is a big term, and it can cover a lot of things, most commonly sales... but salespeople aren't right for every business. So, look at your existing success. What sorts of things bring in the money now... and look to amplify those existing efforts before you go breaking new ground.
You should be looking for someone who complements your existing success and can continue to tell that story, in your existing playing fields, and gradually moving into new areas. I know this was a vague answer, but I hope it helps.