The main rule in Cooking Tale is that you have to cook and serve each customer based on what they order, shown in the bubble box above their head.
You can see the instructions to prepare their order on the Recipe Board at the top of the game screen.
In order to cook the dish, first you need to place the ingredient in the kitchen tool by first clicking on the ingredient to select and then clicking on the kitchen tool to place the ingredient and start cooking.
When the dish is ready, pick it up and click anywhere on the customer to serve. Don't forget that if you fail to take the dish from the kitchen tool on time, your dish may burn and if your dish burns you need to cook the same dish from scratch and put the burned dish to the trash can.
After serving the dish, don't forget to collect the Coins from your counter in order to open space for the new customers. If you collect the Coins consecutively, you can make combos and earn more Coins.
Each customer has a patience level (shown with the five hearts to start) and they eventually get angry and leave if you don't serve what they ordered in time. You can always go back to early levels to replay the tutorial to learn the basics.
Don't miss the opportunity to practice a new dish with Practice Mode. To enter practice mode, click on a level on the map, then click on a dish shown on the menu to learn how to cook it.