Hi Anson,
1.) Choose between Graphic or normal alphnumeric display.
2.) Decide whether it's colour or black and white lcd
a.) colour : CSTN or TFT. likely to be TFT because the price of 2' CSTN is similar to TFT ( TFT is better, mobile phone normally use TFT lcd module ) .
b.) Black & White : HTN. STN etc
HTN is cheaper but view angle and contrast is not as good as STN.
c.) lcd backlight
i.) TFT lcd module : normally includes white colour led
ii.) Non colour lcd : some include lcd backlight. There is reflective ( backlight can't pass through ), transmissive (translucent ) type polariser stick at the back of the lcd glass to decide whether the lcd can light through it or not.
Rogerynt