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.
As others have mentioned Business Development is a very broad term and can be what ever you want just like the last line of most corporate job descriptions...."All other assigned duties"
Depending on the size of your company and at what stage you are in will determine the best solution. Of course that is not within your question but I will assume you are profitable and right on the cusp of taking off.
One idea is to identify your target market and who those customers/partners should be and then do a search for an individual that has experience with those types of customers or even better has specific relationship with those vendors from previous or current roles they were in.
Sometimes business development is hiring someone that can open doors to larger opportunities that can really drive the marketing, branding and awareness to your product/service/business.
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.
It is a bit difficult to answer without having the entire picture, but I will try my best.
If you are growing, then yes, you should definitely hire a business developer (biz dev), that can grow into a biz dev Director.
Generally, they tend to be sociable and driven by success.
I would look for a person that has a point to prove, they are difficult to manage but their drive is second to none.
Hope this helps