Hunting is a fast violent change of direction at least 5 times per second. The fix for this is simply reducing the gain or controlling your headspeed. Other possible fixes are shortening the tail rotor servo arm or using shorter tail blades.

Hunting can damage your model! If you let the t/r hunt, it's just a matter of time before you strip gears or take teeth off your belt. FIX IT.

Here are the things to check when you have a wag. Any or all of them can create the problem.

A wag is a much slower change in direction. I sometimes refer to a wag as "Looking around".

Sticky control rod

Do whatever it takes to make your t/r control rod as smooth as silk. Spare no effort because this is the key to a good tail.

Gyro gain too low

When this is the case, the tail seems very sensitive and moves with the slightest change in rudder or pitch. It overshoots when you let go of the rudder stick. Try raising the gain a few points.

Improper installation of thrust bearings is one of the most common causes of wagging. The illustration shows the proper assembly.
Diagram

You should check this, even if your model was an ARF. Thrust bearings have three parts. An inner race, a ball cage and an outer race. The inside diameter of the outer race is smaller than the inside race. The race that goes on the shaft first has to be a loose fit. If it is tight, the t/r grip can't rotate freely and you will get a wag.

Lack of oil on the t/r output shaft

Electric and gas models are especially prone to this problem. A single drop of Tri-Flow on the tail rotor output shaft could make the difference.

Slow servo

Depending on what type of flying you do, you might be able to get away with a slower servo here. However, it is generally best to use a servo designed for the tail rotor. Even some of these aren't as good as others. You definitely get what you pay for