I always checkout their roster on wechat, if I find an interest when I have time and nearby, I generally message as ask who will be available at my expected arrival time.
(normally within 30 minutes). If my interest looks like being available I might go in. Funny, 9/10 I end up picking another lady.
I do prefer short J-girls with tiny boobs. They just tuen me on, but a do pick others who tweek my fancy.
Very rare for me to walk out without choosing, but it has happenned.