First off, congratulations!!! Second off....BREATHE! Starting out as a new nurse is scary and in all honestly, you probably won't begin to feel comfortable in your new role until about 6 months to a year working. But don't let that discourage you! How long is your orientation? Will you have an assigned preceptor or different preceptors throughout your orientation?
The good thing about med-surg is that you get a taste of everything and you see a variety of things. You will be giving A LOT of antibiotics, antiemetics & analgesics, but you won't be limited to just those medications. Review pre-op and post-op care; since you will be working on med-surg unit you may frequently have patients going for and coming back from surgery. Review physical assessment & lab values. Review some of the medical problems that patients get admitted for. I don't work on a med-surg floor, but I tend to see patients with things like COPD, pneumonia, heart failure, DM, acute & chronic renal failure, abdominal pain, hip fractures, appendectomies, GI surgeries and genitourinary surgeries, but again the things you will see are not limited to this list.
I suggest purchasing Myers' RNotes to carry around with you. And purchase a storage clipboard. You can get them from Walmart for around $10. It opens up and you can store papers and things inside, and depending on the thickness, you might even be able to squeeze in those RNotes, as well. Some of these clipboards also have calculators on the top which can come in handy. Another VERY important thing is a brain sheet! Check out this thread
for some examples, but there are a lot of threads with a lot of sheets. Or you can make your own.