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 Shadow Priest.
Spell Hit (6%) > Intellect > Haste > Crit > Mastery
1. Check for 6% Spell Hit
If you are below 6% Spell Hit, you should reforge your weakest stats (see priority) into Hit Rating or Spirit. Spirit is preferred as it also boosts your Mana regeneration. Reforge for Hit/Spirit until you reach the Spell Hit cap.
2. Optimize Secondary Stats
On any items without Haste or Crit, reforge the weakest stat (see priority) into Haste or Crit as available.