Make sure your radiators aren’t too close to furniture, as they'll absorb all the heat
Touch your radiators (after turning down your flow temperature so they're not too hot!), particularly along the top. If you can feel cooler spots, you should bleed them. Here's how.
Don’t dry clothes directly on the radiator, use a radiator airer or separate clothes dryer
Use reflective foil behind your radiator so the wall doesn’t absorb all the heat
Give your radiators a good clean! If there's loads of dust on them it will act as a heat absorber and reduce their effectiveness
Use a radiator fan to distribute the warmth into the room quicker
Smart radiators: if you want to spend a bit more, get smart radiator valves so you can control your heating room by room.