trick for toilets- get a mr.clean magic eraser or knockoff. cut off a corner and drop it into the bowl overnight. in the morning most of the scale should be gone. magic erasers are microabrasive and therefore may not be for all surfaces, but i don't care if the inside of my toilet is scratched.

i've always used vinegar for hard water stains. one of those sponges with a handle you can put stuff in is nice for cleaning. for the tile /wall inside the shower i use a little dawn dish detergent with the vinegar. if you don't like the smell you can add orange or lemon peels to vinegar. the citrus may help too.

if the stains are really bad lime-away or clr can help.