Tune the guitar to pitch
Capo the first fret
Hold down the low E string at the last fret
Measure the gap at the 7th to 9th fret
Use the correct truss rod wrench
Turn clockwise to reduce neck relief
Turn counterclockwise to increase neck relief
Make small adjustments, about 1/8 turn at a time
Retune the guitar after each adjustment
Recheck the neck relief after each adjustment
Stop if the rod feels stuck or the neck resists strongly
Let the neck settle before making another adjustment
Test play the guitar after adjustment