I just called yesterday for our ADRs and I am a newbie also. Here's what we did.
We used
http://www.wdwinfo.com/wdwinfo/dining/pscalc/dispscalc.html to find our call date. I then looked at a calendar and counted backwards just to double check. A day or two before my call date, DW called the phone number and went through all of the prompts to understand what we would need to do. She made simple notes like 'say English' so we new what each question would be.
Then, we made sure we knew what ADRs we wanted on which day and at which time and made a simple list. For each one, a found a back-up choice just in case we could not get something for the day and time we wanted. We also made sure that we had our reservation number, a pen, and our credit card out.
We used our cell phones because they have the most accurate time and we both started calling at 6:58 or 6:59. When we heard the sound that let us know that we had gotten through, we used those notes to get through the menu quickly and we got to the CM. This was the worst part. It seemed to take forever for her to get our reservation number and info ready so we could ask for the first ADR. When she was ready, I simply said I need CRT for breakfast on X date at 8:00 or so. She checked, said she had it for 8:15; I said I'd take it, then she gave a little thing about arriving 15 minuted early and such and I kind of rushed her through it. She asked me what I wanted next and we did it again.
All in all, I was on the phone for 30 minutes, her computer crashed twice (once losing our CRT, CM, and O'H ADRs), I made 10 ADRs, and got everything I wanted when I wanted it. I did use my backup plan once because she could not find an available dinner reservation at Chef Mickey's on the day I wanted. I gave her a second date that worked for us and she had no problem with that one.
Just relax, know what to expect, and have fun!