Putting garlic in at the wrong time
Cooking garlic is one of the most basic of skills that any chef who went to a culinary institution. For the rest of us non-chefs, not knowing how to properly cook garlic is understandable, but it’s a great lesson to learn. Cooking garlic the wrong way can make a dish taste overly garlicky or not garlicky at all. Your only choices are two extremes, no middle ground.
If you want to achieve the ideal level of garlicky goodness, you need to add it into the hot pan right before the other ingredients cook fully. This will give the garlic enough time to cook while also ensuring your veggies or meats aren’t overdone.