Turning Right at Traffic Lights
If the light is red, or there's already a car in front waiting to turn right, you must wait behind the white stop line.
When the light turns green, move forward taking care not to interfere with the oncoming traffic while you wait for a safe gap. While waiting, you should alternate your view between looking for a gap in the traffic, looking for the light changing, and looking into the road you will be turning into. Try to anticipate when you might turn, and start moving slowly forward so you may turn as soon as safe.
Turning right with a filter light
Some junctions incorporate a filter arrow. You do not need to wait for the arrow to light before turning; as long as you have a green light you can turn when there's a safe gap. If the filter arrow lights, and you're sure the traffic is stopping, then you may turn.
What to do if the lights change to red while waiting
If the light changes to red while waiting to turn, and you are past the white stop line, you must clear the junction as soon as it is safe. Be careful of pedestrians in the road you are entering who might have a crossing light before you start turning, and be prepared to stop for them.