3. Use vinegar only where there is limescale
Vinegar has a narrow job and a lot of misplaced fame. It dissolves calcium carbonate, so it is excellent on kettle scale, shower heads, tap aerators, the glass door of a dishwasher and the cloudy film on glassware in hard-water areas. It does very little on grease and nothing on carbon.
For the kettle, half-fill with equal parts white vinegar and water, bring it just to the boil, switch off and leave it an hour. Pour away, then boil twice with clean water and discard both — the residual smell is the reason people abandon this method halfway.
For tap aerators, unscrew the nozzle, drop the parts in a cup of neat vinegar overnight and brush them with an old toothbrush. Flow usually returns to what it was when the tap was new. A fixed shower head that will not unscrew gets a sandwich bag of vinegar rubber-banded around it for a couple of hours.
Now the limits, because this is where vinegar does damage. Keep it off natural stone worktops, marble, travertine and unsealed grout — the acid etches them and the dull patch does not polish out. Keep it off cast iron, which it will strip and rust. Keep it away from rubber seals on appliances if used neat and repeatedly, since it hardens them over time. And skip it on waxed or oiled wooden worktops, where it cuts the finish.
For hard-water spotting on a stainless sink, a half lemon dipped in salt is easier than vinegar and smells better.