To learn how to cook deliciously, you don't have to go to a special course - there's the Internet, which is full of recipes for every taste and professional chefs who are willing to share their experiences and help you avoid the most common mistakes. Here we will talk about the latter (even if you know all this, do not forget that there are people who have just started their culinary journey).
Trite advice, but still: clean up while you're cooking, otherwise you'll have Armageddon waiting for you at the end, which will take a very long time to clean up. And not all dishes require standing over them all the time, so it's fine to find time to wash dishes while there's still room in the sink (or load the dishwasher).
The most dangerous item in the kitchen is a dull knife. That's right. First of all, you won't cut soft foods, you'll crumple them. Secondly, to cut something tough with such a knife, you need to put a lot of effort - if the knife slips, there is no way to avoid injury.
Again about the knife. The way the chefs cut food quickly, accurately and smoothly evokes admiration and a desire to immediately repeat this at home. But this is a case where you have to act with feeling, with thought, with the arrangement - they did not learn this right away too. First of all you need to hone your accuracy and precision, and then learn to do it fast. This is not a competition, after all.
If you've already salted a dish and added all the spices you have at home, but you feel that something is still missing, try adding something sour (lemon juice, lemon zest, lime juice, balsamic/apple/wine vinegar). You'll be surprised how brightly the dish will play with new colors.
Do not put pressure on the cutlet, which is fried in a pan, trying to speed up its cooking. It won't taste any better.
People won't come after you in uniform if you change the recipe a bit (this doesn't apply to baking, accuracy is important here). Don't like the garlic? Don't put it in (or reduce the amount). There is a little nuance: the first time cooks are advised to cook the dish exactly according to the recipe. If it turns out well, you can think about what to change in it (for example, reduce the amount of sugar or take a different flour).
It's a big mistake to think you have a luxurious eye and ignore the kitchen scale. This is especially true for baked goods (and even more so for those you haven't gotten your hands on yet). Give or take 50 grams, and things can go wrong. And then you'll be thinking about where exactly you went wrong.
If the recipe says you want fresh mushrooms, use fresh mushrooms (even if you have to go to the store for them, and you have a jar of pickled ones at home).
The microwave is not the enemy.
Don't assume that preheating the oven is just a recommendation, not a rule that must be followed. If you only turn on the oven the moment you put a dish in it (and it was written in black and white in the recipe about preheating), it will have a negative impact on the texture and appearance of the finished dish, as well as on the cooking time. For example, the cookies may turn out too hard and flat rather than airy, and the cake may not bake evenly.
The same applies to pans. Putting food on cold ones is a mistake. At the very least, they need to be warmed up. And if you're cooking white meat, fish, vegetables, or steak, they need to be heated. If your pans don't have a heat indicator, drip cold water on them.
Speaking of cookies. After you knead the shortbread dough, refrigerate it - this will prevent unnecessary brittleness and reduce the chance of burning.