First you'll want to ensure your guitar actually needs adjustment before you start adjusting anything. Assuming you already did that part, here are the steps. To Add Neck Relief: Loosen truss rod by 1/4 turn. Let set for 10 minutes. Recheck. Repeat until satisfied.   To Subtract Neck Relief (Straighten): Tighten truss rod by 1/4 turn. Let set for 10 minutes. Recheck. Repeat until satisfied.