Take a notepad or binder and a pen - use it to write things that are important - a couple of notes not an essay. Ask questions back to the people who are interviewing you - relevant ones though like who you will be working with/for, main responsibilities, etc.
Find out as much as you can about the company on the internet, who their main customers are (very specifically, such as industry or if it is the public who their demographic is) how they make money, the history, who owns it.
Keep in mind that in BD, you are there to generate business, they want you to make them money, tell them how you are going to make them money, if they think you can make them money then they will employ you, if they don't then they won't.
Good luck :)