There is no guaranteed way to permanently reduce insulin resistance. That would effectively mean a "Cure" for many people.
However, we do know that exercise and avoiding excess body fat accumulation are two things that have a strong chance of reducing insulin resistance.
The other approach is to avoid the causes of hyperglycemia as a result of insulin resistance. Many people on this forum choose to restrict or monitor their carbohydrate intake as they find that has significantly positive results on avoiding hyperglycemia. However, it's important to note that other factors (medication, stress, other health conditions, etc) can also contribute to hyperglycemia.
If you're of a normal bodyweight and exercise regularly then you may be one of the unlucky ~20% of people who are of a normal BMI, but have insulin resistance. Lifestyle intervention may have less of an effect on you that others who may be very obese.