Pay attention to what you are told. No Chef likes to have to repeat himself.
Pay attention to detail.
First day? You can expect to do a lot of listening and watching. Depending on the Hotel, much of your day may be spent in orientation and Hotel standards.
Work hard. Keep your mouth shut and your ears open, don't assume anything.
Get a small pocket notebook. Write things down... recipes, standards. Study the standard recipe book. Get to know your station like the back of your hand, and always, always cook like your grandmother has brought all her friends to eat your food.
You've got an in on the ground floor, which, in my opinion is the only way to start in this business. You're going to be the new guy, and you will be doing a lot of grunt work. Expect a lot of repetive, "boring" work. You're going to be plating salads, slicing meats, peeling fruit and cutting vegetables.
You may be too young to remember the original Karate Kid... but it's "Wax on, wax off" time.