First, switch off your heating system and ensure all your radiators are cooled down. Then, open both valves up on each of the radiators and turn the heating on.
You might have to enlist the help of other family members in the household, but all the radiators need to be examined so you can work out when they heat up and the order in which they heat up.
If you want a particular room to heat up quicker, you should open the lockshield valve on the radiators in that space a touch more.
For the opposite effect in rooms that perhaps aren’t used very often, you can delay the heating process by tightening the lockshield valve slightly more.
More detailed instructions can be found in our Advice Centre blog, Here’s How To Balance Radiators.