Reforging allows you to modify the secondary stats on your gear. Use this guide to determine the best strategy for reforging your stats so that you can optimize the performance of your Destruction Warlock.
Intellect > Spell Hit (15%) > Mastery >= Haste > Crit
1. Check for 15% Spell Hit
If you are not at or above 15% Hit, then reforge your gear until you are at the Hit cap. On any gear without Hit, reforge the weakest stat (see stat priority) into Hit Rating or Expertise. Do this until you are at or slightly above 15%.
2. Optimize Secondary Stats
On any gear without Mastery or Haste, reforge the weakest stat (see priority) into Mastery or Haste as available.