When you start your own business, most people are not used to interviewing potential employees, because not too long ago you were just an employee yourself.
You have to remember that the person being interviewed is probably nervous, so try and write your own set of questions, rather than only going the general what-are-your-strengths-and-weaknesses route. Ask the interviewee questions that would actually pertain to your business, if you work in an office that always has people walking in and out or loud music, ask your interviewee if they can concentrate in that type of environment, many people cannot, and although you may do your best to accommodate someone who you think is good for the position, if that someone doesn't adjust well, they may leave, or be unhappy.
Also when interviewing, make sure you try your best to make the interviewee feel comfortable, the environment for an interview doesn't have to be uptight and by the book. I've had interviews where the interviewer asked what type of music I preferred or what my favorite movie is, questions such as these allow you to gauge the interviewees personality better to see if they are a good fit for your company, it opens up the invitation for chat, which can put the interviewee at ease.
I myself don't have much experience being the interviewee, and very little being the interviewer. I've only had a few jobs, and I didn't interview many times before I found somewhere I fit in, but there is one interview that will always stick out in my mind, and it's basically what not to do when conducting an interview. It could have been the uncomfortably quiet office that I walked into that didn't help put me at ease, but the company owner who was interviewing me also was cold and inviting. Part of the interview required me to do a basic math quiz, after the test, the owner came in to score it, I had got all problems but one correct, and the owner's comment was, "Well, you're not dumb." I pretty much wanted to leave right then, but I stuck around for the remainder of the interview, basically being given the rundown on how operations work. I left knowing that if I had got offered the position (even though the pay was higher than I was expecting), I would not take it. I was offered the position within the next week, I declined.