Forgive me if I repeat what others have said. It helps me keep a train of thought to write it as it comes to me.
If they don't offer bottled water, take a bottle or two. I was told to always eat a light breakfast before chemo. Take snacks if you think you'll get the munchies from sitting there for 3 hours; I'm rarely hungry but sometimes I'm snacky and I usually grab a cracker or two. Don't take anything spicy until you know how your stomach will react to chemo. Water, water, water. You want to stay hydrated. This is a BIG deal, as I think someone else mentioned.
Different people respond differently to the same medication so you will hear about different experiences, and I'm guessing that different infusion centers have different ways of doing things, but I'll give you an idea of how my sessions go. If they gave you Lidocaine cream, put a nickel sized glob of that on your port about an hour before you get there. Cover the cream with a small piece of plastic wrap, just to keep the cream in place. The cream is to numb the area so that you don't feel it when they insert the port needle. Don't worry if you forget - they will probably have numbing spray on their carts. Plus I know lots of people who never bother with the cream or the spray and say it's not a big deal. My chemo nurse, who has been doing this for about 20 years and is awesome, always tells me to take a deep breath and then when I let it out she pushes in the needle thingy. Never feel it. After you're set up with that, the nurse will take blood from the port - maybe not the first time but for all future visits - and then you'll wait to make sure your blood levels are ok for chemo. Those blood levels - especially platelets and white blood cells - may be a moving target later. If your levels are ok, then they will hook you up. And then you basically sit there for about 3 hours. Boredom can play a big part.
Important ---> wear a button-down shirt or a v-neck t-shirt that makes it really easy to get to the port. Wear comfortable pants that are easy to get on and off. If you need to go to the bathroom, you'll be dragging your IV pole with you and you don't want to be fumbling with tight jeans and such. Just my opinion, your mileage may vary.
I find that I am often a little cold so I have a lightweight blanket in my chemo bag (a backpack that I dedicate to stuff I might need during infusions). I also take a Kindle or iPad, and an iPod that I use just for meditation. If your infusion center has good wi-fi you can watch a movie or whatever. I usually just read. You shouldn't need any medication - they will give you anti-nausea meds in your IV so you won't need those until later, if at all.
Did I mention water? Water, water, water. Can't say it often enough. AFTER the infusion, keep up with your water, not only to keep from getting dehydrated but also to flush the chemo out of your system.
When the infusion is over, they will hook up the fluid lines to a pump. There are different kinds of pumps. Mine was one inside a fanny pack. You'll live with the pump for 2 more days. It's not as bad as it sounds, at least I don't think so but it does take some getting used to. I've heard that some people shower with the pump sitting outside the shower but I don't think I could safely do it. To be safe, shower/bathe before you go in case you have to go 3 days without.
Don't think of chemo as poison; it's magic juice.
I'm usually very sleepy for a few days after the infusion. The first time was the worst, maybe because I had so much anxiety going into it that I crashed afterwards. You may experience nausea and probably already have anti-nausea meds. If not, fill the prescription before the infusion. You may experience constipation and the anti-nausea drugs might make it worse. Zofran especially can cause constipation; I had to toss mine for that reason. If you live in a medical marijuana state, consider getting a vape pen; it stops the nausea almost instantaneously without the pesky side effects. You can get a vape cartridge with a dose of THC that's so low that you'll wonder if you got ripped off - but you'll know it's real when the nausea hits and 1 good puff does the trick. Back to the constipation, try glycerin suppositories (drugstore) if it gets really bad. You might want to consider taking Colace or another stool softener starting a day or two before the infusion. It's a trial and error kind of thing. A lot of people use Miralax daily. If you want something more natural, try Smooth Move Tea
by Traditional Medicinals (don't drink too much, it can be powerful) or Calm
magnesium powder. I buy them both at Sprouts or on Amazon. You may get hemorrhoids; I've found that coconut oil suppositories do wonders for me (found that tip on a pregnancy forum). I make my own; feel free to PM me if you want more info about that.
This is all from my own experience and you may not have any of these side effects and/or the remedies I've found may not work for you. I'm not a doctor or nurse, just another patient sharing my story.
Wishing you peace and an easy chemo experience. It will be ok ... you can do this.
P.S. Did I mention water?!?!