Wow that is so special and such an honor to be able to be there with your friend! Good for you! #1 Rule--don't complain about anything and don't let anyone around her complain. After baby arrives take lots and lots and lots of pictures so neither the mom or dad have to worry about missing a precious moment.
Bring an extra headband and chapstick. I packed like I was going on a 3-day Mt Everest excursion and in the end, only ended up using the chapstick I had packed. You could help them a bunch by having your friend give you a list of all the friends and family she'd like you to call after the baby is born. Other than that, there's not much to do.
I didn't get hungry, the ice chips were actually quite refreshing (more than I thought they would be)...however my husband did get hungry and bored...hindsight 20/20, I wish I had used a doula or had a girlfriend in there with me. Just 'be there" for your friend so that her husband can leave for a bit if he needs to get something to eat or go to the bathroom, and she won't be alone. After the REAL contractions started to kick in, I didn't want to talk to anyone and didn't really want anyone talking around me, so don't worry about trying to keep her entertained. Just hold her hand and gently rub her head and no matter what she asks you to do, just say "OK" and try to do it (i.e. if she says "where the h*** is the darn anastethiologist, nurse, puke bag, etc??!!" just say you'll go find out!