The best way for a perfect fork set up.
If you have the correct sag and are either, blowing through all your travel easily or not using enough, then you need to experiment with Volume reducers. Volume reducers do just that, they reduce the volume of your air chamber. When you reduce the size of your chamber, you will cause the fork to 'ramp up' quicker, basically becoming progressively harder to compress the fork further in the travel.
If you're using all your travel too easily, adding spacers will prevent this. On the flip side, if you're not using enough, removing them is the way to go.
Please note: There's no set rule for how many to add. It comes down to your own personal preferences and some trial and error.