There are a few different solutions that can prevent your bathroom mirror from fogging, though the method always remains the same. Whether you use vinegar, hair conditioner or a solution you buy at a hardware store, you will need to first make sure that there are no streaks on the mirror.
Step 1: Clean Your Mirror
Clean your mirror thoroughly with with a soft rag using a cleaning agent designed for glass. It is important to make sure that there are no spots, streaks or marks left over after it is cleaned, because any extra marks will cause additional viewing problems with the mirror after the process is complete.
Step 2: Add the Solution
With your other soft rag, add a small amount of vinegar, hair spray or de-fog solution. You may use any of the three, but do not mix them together.
Use your rag to rub the solution over the mirror, taking your time to make sure you have covered the whole mirror. Let it sit for a couple of minutes then wipe it off with your third clean rag.
You will need to repeat this process every other month to make sure that your mirror remains fog free.