Always use the type of fuel that is recommended for your appliance.
Always use the best quality fuel that you can afford. There will be less ash and the calorific value (heat content) of the fuel will be higher.
Ash and clinker - Use the riddling device and a poker to clear ash and clinker that collects above the fire bars. The appliance will not function to capacity if the grate is clogged. Don't allow the ash to build up in the ash pan. This can lead to damaged fire bars.
Get your chimney swept regularly (at least once a year and twice if burning wood or house coal).
Follow the manufacturers instructions on maintenance. On closed appliances clean the throat plate and check all door seals to ensure that they are airtight. Any boiler surfaces should be scraped clean every heating season. Although some appliances can be used with the door open, they will be more efficient with the door closed.