My big advice is this: Just match their tone. If they sound laid back, be laid back. If they sound go-getter, then be go-getter, but don't overdo it.
This is what they want to hear:
1. You're using PPC to drive traffic.
2. You've done it before, or you're studying with PPC-Coach, or read a lot of Wickedfire, or both.
3. You're using PPC to drive traffic.
4. You're using PPC to drive traffic.
If you're a Noob, say so if they ask. But even so, be confident.
Your actual interview will go like this in a nutshell.
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AM: Hey.
You: Hey.
AM: So you wanna do business with (PUT NAME OF COMPANY HERE) How did you find out about us?
You: (ANSWER HERE: HEARD ABOUT YOU ON PPC-COACH, OFFER VAULT, SUCCESSFUL PPC PAL TOLD YOU, FORUMS. ETC)... I think that I could do well. I'll be using PPC to drive traffic to your offers. Is that going to be a problem?
AM: No, not at all. Tell me about your sites.
You: (Tell them about your sites. Have at least one up. If you don't have one, get a WP blog with a decent design, and fill it with something. You don't have to, but it's good to have SOMETHING up, though not a neccesity.)
AM: Wow, that's great/cool/nice.
You: SO you're OK with the PPC?
AM: Yeah.
You: Great/Cool/Nice.
AM: We'll, I'm going to approve your app, and you'll get our site info with it in a few days. I'll be assigning (XXXX) to you, and she'll send over a letter and introduce herself. OK/Cool/Sound good?
You: OK/Cool/Sound good?
AM: OK, congrats, and have good day.
HANG UP.
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Another thing, don't be afraid to pick up the phone and call back if you get rejected. I called more than a few of my first rejections back, and said, " I don't understand. Don't you accept PPC traffic for your campaigns?" They took me on the spot. Go for it, and remember, there are hundreds of companies. They need YOU, not the other way around.
Good luck to you.