The best way to achieve the perfect temperature dab is with a precise thermometer. These thermometers measure the temperature of your dab nail and will allow you to always find the optimal temperature to hit a dab out of your rig. Many of these are Digital IR Thermometer, but some work with direct contact.
While everyone will find a different optimal temperature for dabs, Many users will use the following numbers:
Low Temp: 400°F - 500°F (Best flavor and smoothest hits)
Mid Temp: 500°F - 545°F (Good taste and optimal efficiency)
Standard: 545°F - 570°F (High efficiency of concentrate)
High Temp: 570°+ (Complete vaporization of concentrate, may be burnt)