It varies with each buyers.

Follw a logical route based upon the point where we meet the clients, so we reduce time wasted and fuel. The price, etc. is not important.

Convenience.  Start at point A and end up at point B.

Area.

Now if only four homes in same area, it is worst, best, worst, worst, ugly, stinky.

Treat all of them the same. Schedule appointments until your schedule is full.

Geographically.

A sequence that makes sense for drive time

I try to map them so we are not jumping all over the place.  

I strictly schedule them in the most logical fashion, based on location.