Choose a weak acid and its conjugate base, or a weak base and its conjugate acid
Decide the target pH and buffer capacity needed
Calculate the required amounts of each buffer component using the Henderson-Hasselbalch equation
Measure the required volume of distilled or deionized water
Dissolve the weak acid or weak base in the water
Add the conjugate base or conjugate acid gradually while stirring
Check the pH with a calibrated pH meter
Adjust the pH if needed by adding small amounts of acid or base
Bring the solution to the final desired volume with water
Mix thoroughly
Recheck the pH after mixing
Store the buffer in a clean, labeled container