Start with a full test of the water:
FC
CC
pH
T/A
CYA
CH
Temperature.

Get a baseline. If your water's very acidic or alkaline you'll have to fix it.
But, unless you have reason to suspect metals, chlorine's the place to start. If your pH is high and your CYA is low, pucks are a good because they address both. But LC/Bleach is ALWAYS good.