Some people call it a "spark hook test". It's a series of runs (with cool down in between), where the advance is started low, and increased a couple of degrees each successive pull. On most engines with decent chamber design & quench, power will stop increasing at some point, slowly decrease, and eventually end up knocking. Go through the data, and pick the minimum spark that gets you near the power peak. AFR should be about 12.5 at peak torque, and about 13.0 around peak HP before you try this. All the better if your ECU uses a calibrated knock sensor and will pull timing when it hears detonation.
