Most dilution mistakes happen before the feed reaches the plant. Read the product instructions and work out the amount needed for the volume you are actually mixing.
A dose for a large watering can should not be guessed into a small bottle. Use measuring equipment that makes the small quantity practical, and keep it separate from food preparation.
Label the mixture
Write the product name, dilution and mixing date on the container if it will not be used immediately. Do not leave an unidentified bottle beside plain water and expect to remember the difference later.
Use the feed only on suitable plants at an appropriate stage of growth. A stressed, resting or persistently wet plant needs its conditions reviewed rather than receiving a stronger mixture.
If several products are part of the routine, check whether their nutrients overlap. 'A little of each' is not a dilution instruction. Keep the original label available so you can repeat the application or explain exactly what was used. A feed that is easy to measure consistently is easier to manage than an improvised dose that changes every time.
Related reading: Liquid Fertiliser: Application Methods and Dilution.