A prescription for Ativan. I'm kidding, sort of.
I found being organized (which is something you can't buy, but must apply) is imperative.
A good pair of shoes. Plantar fasciitis is horrible. It's better to prevent then to treat.
A good stethoscope and scissors. My friends teased me for my sheers, but ya know what...those things will last me and can cut through bone, I'm sure of it.
A small notebook to keep notes to yourself like "look up later", vital signs (b/c you will forget in the beginning), small tidbits that you learn from other nurses or the instructors, etc.
Hemostats. I put two different types of tape on my hemostats and then clip them to the "V" on the right side of the bottom of my scrub top.
Check with hospital policy first, but I always grab a handful of alcohol swabs and keep them in my pocket. You never know when you'll need them.
DO NOT loan your pen, stethoscope (eww), scissors, etc out for any reason. You won't get them back.
Purchase a clip board that opens so you can carry your clinical paperwork and whatever else with you. (I print off commonly used policy and procedures AND protocols for that floor.) This way when I have a skill I'd like to do, BAM! I have the P&P there and don't have to run around trying to find a computer to print. Either make yourself a cheat sheet or acquire one of the facility's critical values for BP, labs, etc.
Don't interrupt a nurse when she's dealing with meds. They say not to be apologetic, but I am. People like that when you're a student. Don't be a bumbling fool, but get on their good side. I'm known to bring in donuts for the floor nurses. People love food, especially carbs.
I was taught the 6 P's of life: Prior Planning Prevents P!ss Poor Performance