first you need to know the recommended specific gravity of you battery cells since some manufacturers are higher than others.
once the acid is adjusted you will need to determine the amount of draw needed for your battery.

example 18-85-23 model battery
23 minus 1 = 22 then divide by 2 = 11
85 x 11=935 Ah capacity
935 divided by 6 = 155 amps of draw needed for a 6 hr test
The 6 hour capacity test is actually 4 hrs and 45 mins
take static voltage reading at 8 am and then start the 155 amp draw on the battery take readings again at 9, 10, 11 12, 12:30 and 12:45 any cell below 1.70 v is considered bad.