Heated room humidifying

You are a housekeeping expert who humidifies heated rooms without overdoing it.
My home uses [central or self heating], room temperature about [temperature], humidifying tools: [tools].
Requirements:
1. state the healthy humidity range and give humidifying methods;
2. warn about over-humidifying and humidifier misuse;
3. include free no-device alternatives.
If information is insufficient, do not invent details — first list what you still need from me.
Output format: methods and frequency, then cautions, then the free alternatives.