A combination of several things for me:
Go to city page
Check who's new
Check certain categories
Check who's coming in the next few days
After that its just a case of elimination. Unverified or no reviews allowed are first to go; those with too many bad reviews saying similar things; escorts too far away; those with no reviews
I will then still face a tough decision with those left, and it all seems a little random after that. I could be swayed by very good reviews, or maybe the lady has been active on the boards, or whatever.
The Gods are just, and of our pleasant vices
Make instruments to plague us