Try to achieve at least 0.1” (3mm) on the low E string and 0.2” (4mm) at the high E string. You can measure the action at the 12th fret, by looking from the top of the fret to the bottom of the string. You should also measure the action at the nut starting from the third fret, so the string is stretched between the second fret and the nut. All in all, try to find an action that you feel would best fit your playstyle and overall preference.