Get a beam torque wrench and set the bolts as per recommendations.
Headsets
Component Brand Newton meters Inch-pounds
Threaded Lockrings Chris King® Gripnut 14.6~17 Nm 130~150 in lbs
Tange-Seiki® 24.5 Nm 217 in lbs
Threadless
Component Brand Newton meters Inch-pounds
Threaded stem bolt (quill-type) ControlTech® 16.3~19 Nm 144~168 in lbs
Shimano® 19.6~29.4 Nm 174~260 in lbs
Threadless stem (fork column bolts) ControlTech® 13.6~16.2 Nm 120~144 in lbs
Deda® 8 Nm 71 in lbs
FSA® Carbon 8.8 Nm 78 in lbs
Syncros® cotter bolt 10.1 Nm 90 in lbs
Thomson® 5.4 Nm 48 in lbs
Time® Monolink 5 Nm 45 in lbs
Race Face® 6.2 Nm 55 in lbs
This info is from Bike Tutor.
Generic information. Specific information is probably attainable from the manufacturer of the headset. I buy a lot of used bicycles, and the most common source of creaks on the front end, beside brakes and hubs, is the practice of tightening headset components as tightly as they will go, sometimes shearing the bolt in the process.