Stress their expertise as the reason you are calling. Made your contacts. Now it's time to meet. Be on time, or even a little early. A twenty-minute meeting passes quickly.
Efficiency is everything.
To make sure all your questions are answered you may want to e-mail your questions before the interview. This gives your contacts time to prepare thoughtful answers. Take careful notes during the meeting so you can go back and refer to them later. After your meetings follow-up with thank you notes. This shows you're grateful for their time, but also leaves a positive, professional and courteous image behind.