Nice idea...
I choose what crystals to look at when I'm reading for someone else. (email readings).
I have a small selection of "reading crystals". There's always a clear quartz there somewhere... and usually my Turqouise mini Buddha (Hotei - patron of fortune tellers).
The rest varies according to mood.
A small Obsidian palm mirror...
A small Smokey Quartz skull, Opalite skull or Amber skull...
When reading face-to-face - I'll have crystals on the table only if there's space for them.
(so if reading at home yes - if elsewhere, depends).
Crystals in my pocket - these I choose purely by mood/state of wellbeing.
So - recently, as I've been feeling more vulnerable due to back pain issues - I've been carrying my Black Tourmaline stick around alot in my pocket.