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 Discipline Priest.
Intellect > Spirit > Mastery > Crit > Haste
1. Optimize Spirit
On any gear without Spirit, reforge the weakest stat (see stat priority) into Spirit. Do this until you have enough Spirit to provide you with just enough Mana to survive the typical PvP encounter.
2. Optimize Secondary Stats
On any items without Mastery or Crit, reforge the weakest stat (see priority) into Mastery or Crit as available.