Simple - don't forget to breath. Take it one day at a time. Bring your own music. Ask for blankets if you are cold (they like to keep the machinery cool). I took antianxiety meds and slept through many of my treatments. The first 3 weeks should be a cookie cutter then the side effects will start to kick in.
In spite of what a few nut cases say, you will have no sensation of much of anything during the actual treatment. Be nice to the radiation therapists - they didn't give you cancer (and truth be known, they feel bad about it - I know, I asked them). ALWAYS check the computer monitor to insure that YOUR name is on the treatment plan. One gal here got irradiated for prostate cancer because the previous patient didn't show up. Oops!

IMPORTANT - Insure your neck is clean and free of any oils or any other substance. They can act as a bolus and increase the skin damage to the neck at the beam entry points.

Have your meds ordered and lined up BEFORE you need them. You really don't want to take a trip to the ER on a Friday night...

I commuted an hour to an hour and a half (each way), 5 days a week in heavy SF Bay Area traffic to go to a CCC (there is a local radiation treatment center a block from my house)- my wife or other voluteer drivers drove me - I didn't. If you have a car get a handicapped placard. After three weeks you'll be crawling into treatment on your belly.