Choose the buffer system you need
Select a weak acid and its conjugate base, or a weak base and its conjugate acid
Decide the target pH
Calculate the required acid-to-base ratio using the Henderson-Hasselbalch equation
Measure the needed amounts of buffer components
Dissolve the components in distilled water
Adjust the pH with small amounts of acid or base if needed
Bring the solution to the final desired volume
Mix thoroughly
Verify the pH with a calibrated pH meter