There is no set method. The end goal is to have good blending of the sub with the speakers.
Since the sub is not particularly tough, it is critically important to find the optimal location for it.
Crawling for bass is an easy way to dial in the location.
Based on the measurements from this
review, initially set all crossovers at 100Hz.
From here start tweaking. That said, don't go below 60 Hz for mains (based on measured FR), 80 Hz for center, and 100 Hz for rears (article's FR measurements for center and rear are practically meaningless).
When set correctly, you should not be able to tell that a sub is playing.