The list above is great. The only things I'd add (or expand upon):
Know the company, and the types of responsibilities you'd be expected to assume in the position. I interview people pretty frequently, and it's amazing how many people respond with a blank look when you ask "What makes you want to work here?" or "What are the biggest challenges you think this industry has to face in order to grow?" It's always a great idea to do some in-depth research on the company, find out what challenges they face, and then use that in your answer. For example, a quick Google search on "OG&E" yielded this
article. Great opprtunity to talk about wind power, and the challenges in "going green."
Use eye contact, clear speech, and smile when appropriate. Remember, some of the people that are interviewing you will also work with you, and they are also evaluating your personality. Nobody wants to work with someone who has no sense of humor, mumbles, and won't look you in the eye.
Be honest. A lot of interviewers will ask you what your biggest weakness is (or some derivation of the question). Be upfront about this, and for God's sake don't use the old "I work too hard" answer. If you don't have 100% of the experience they're looking for you both already know it, so don't try and skate around the issue. Instead use an example from a previous job. For example, "In my last position with company X, I didn't have a great deal of experience dealing with widgets. To overcome this, I took widget night school. The end result was I became an expert in widgets, and everyone in the sales department looked to me to solve technical problems. I can do the same thing here."
Good luck with this. Interviews can be nerve wracking, but go in there believing you're the best person for the job, and that they'd be lucky to have you.