Hello and welcome to the world of cooks and the lifestyle it entails! I personally love the lifestyle and I love to cook and am very pleased when I see customers smiling and enjoying our food.
As a first timer, and probably in your first few shifts you will be put into one of several roles. These could be a dishwasher, a pantry or cold line cooking position, or a prep cook position. You will most likely not start on the line cooking food to order. That is where the big dogs are and they have a lot of experience with what they do. This is a position to strive for.
I won't go into dish washing as that is fairly self explanatory. If you are in the pantry, you will probably spend your first shift learning the components and how to make salads and other cold appetizers. Don't think this is below you or that you already know how to make a salad. This is the basis for all of your cooking in the future - you take making a salad seriously and that will translate everywhere else. So this would be the start of your cooking experience if this is the position that you would land in. You may be here for a month or two or longer depending on how well you do and how fast your are while making consistent and clean plates. From here it is possible to get a chance to work on the hot line once the chef has seen your chops and can assess how well they can train you to put together the components of a entre such as grilling a steak to the proper temperature and plating it how the chef wants you to, and do that every time, clean and consistently. Consistency is huge! Your customers expect the same plate as the one they loved last time they were in your restaurant.
If you are placed as a prep cook your experience in the first few days will be a bit different. Here you will have a list of ingredients that need to be prepped and cooked for the coming service (dinner, lunch, breakfast). Someone senior will tell you to start with something simple like peeling and cutting carrots in a specific fashion. Don't be discouraged if you feel you are doing work that a monkey could do. You are starting to learn the building blocks of cooking. You will learn knife skills which are very important and you will begin to understand why the specific ingredients go into a dish and why you are prepping them in a certain fashion. You will be given more complex tasks after you have shown that you have the simple things down and can do them expediently and correctly.
This is the basis for the day in the life of a shift of cooking. The next day will be much the same as the first but there are always little ways that make each day a bit different. I would suggest, if you like this line of work and it's okay if you don't now is the best time to figure that out, that you keep your ears and eyes open and watch what the other cooks around you are doing. Ask questions if you don't understand what you need to do, even if you have to ask ten times. It's better to get it right the first time then waste time and money by not prepping or plating foods as they need to be done.
I would also spend a bit of time learning on your own outside of the kitchen if this line of work is something that you think you would like to do. For example, you might want to go on youtube and find out more about knife skills and the various cuts that you will want to know. Hell, you might not know how to properly hold a chef knife in which case I think youtube is a great place to learn for rudimentary cooking skills.
Always remember - you're not an idiot for not knowing how to do something. Others may make you feel like this but we all have been where you are now. You just haven't had the experience of learning what others already know. Nothing more, nothing less.
I wish you the best and if you have more questions feel free to pm me. I love the site and the people here are great!