Heat vinegar until hot and pour into a spray bottle.
Add the Dawn dish soap. Put the lid on and gently shake to incorporate.
Use and be amazed at how well your bathroom gets cleaned! For tough soap scum build-up, spray the mixture on and allow it to sit as long as overnight. Then, scrub and rinse.
Notes
You will only want to lightly spray the surface you are cleaning as this cleaner is quite sudsy and if you get spray happy you might get frustrated at the effort it takes to wipe it all up!
I had originally posted this as equal parts Dawn dish soap and white vinegar. But since then have discovered that 8 oz. of Dawn works just as well and also produces fewer suds, making it easier to wipe clean.
For a natural alternative to Dawn dish soap, use Sals Suds. This is what I now use instead of the Dawn.