Job interview; questions I can ask a potential employer?

Iv found that it is important to maintain control in an interview.

One way is to ask certain questions on a general basis, especially if you are inexperienced...

I usually wing it but Im a bit nervous about this interview, its for sales and administration.

Could anyone add to my list?

who are company competitors

specific services provided by the company

what are the branding or product initiatives

type of client base the company holds

type of software used by administration

Are there any other question I could ask, I need something thats an eye opener....