You need to know the schedule (how often, how long each time). You need to know what types of drugs he's getting, what are the expected side effects, and what to look for if he's having a bad reaction. You need to know who to call and when to call if there are problems. You need to know how many cycles (treatments) until they retest, and what they will be looking for. You need to know what will disqualify him from chemo (blood count and fever are 2 common ones). You need to know what meds he'll be taking after chemo for nausea, pain, and other things, and how to evaluate his condition.
They will give you a booklet with nutrition ideas, but it's mostly hits and misses unless he's on a special diet. You should probably have some nutritional drinks on hand (ensure or the like) in case he's feeling really nauseated so that he can get some calories into him easily.
Most people I've heard don't have major side effects their first chemo, but they do build up and get stronger as you go along.
Let me know if you have other questions. My husband has done a LOT of chemo in the last 10 months.