Physically measure the distance to insure accuracy. Accurate measurements here are critical in determining the image quality of the speaker system. Distance between the speakers will be determined by the distance to your listening position and the particular speaker you own. Use this measurement, if available and your room permits. Remember that any recommendation is only a starting point.
Experimentation is always the key to finding the right placement.
Select recordings with which you are very familiar. My personal preference is toward simple recordings with good, even spread across the stage and a strongly focused center image. Some speakers sound best with little or no toe-in, others may require a great deal to perform properly. I recommend using a carpenters level to achieve correct level. Remember to check both front to back and side to side.