One of the most common mistakes people make when deep frying is not having enough oil in the pan. If you don't have enough oil, your food will stick to the bottom of the pan and it won't be as crisp. Another mistake is not heating the oil hot enough. The oil should be between 350-375 degrees Fahrenheit. If it's not hot enough, your food will absorb too much oil and be greasy. Finally, people often overcrowd the pan when deep frying. This lowers the temperature of the oil and makes for soggy, oily food. So make sure you have plenty of space in your pan before you start cooking!