1-Don't block the air flow from a radiator, Don't use radiator covers, don't hang washing on them, don't block them with furniture. The rooms will heat more quickly if you avoid doing this.
2-Carry out your own maintenance on your radiators, bleed them, this releases air build up in them. They will work at there full potential and the heat being distributed evenly.
3-Keep them clean, dust free in all areas, even the hard to reach parts need to be dusted. You need to turn your radiator off before tackling the cleaning. You can buy radiator cleaners that reach these difficult places or you can make your own, this will prevent a build up getting into internal fans as this may prevent the transfer of heat.
With the energy prices rising these hacks will prevent you wasting unnecessary energy.