Right-of-way, intersections and priority rules
Priority rules
At an unmarked intersection, the default rule is to give way to traffic approaching from your right. Priority signs change this: a priority-road sign or a major-road layout means traffic on that road has priority; a YIELD or STOP sign means you must give way. At a roundabout, entering traffic gives way to traffic already circulating unless signs or signals say otherwise. When turning left, you cross oncoming traffic, so you must give way to vehicles coming towards you. Pedestrians on a marked crossing have priority. At a T-junction, the road that ends normally gives way unless signed otherwise.
Worked example
You arrive at a small unmarked crossroads at the same time as a car from your right. There are no signs or lights. The car is on your right, so you give way. Even if you arrived a second earlier, the right-hand rule still applies because there is no sign making your road priority. You wait until the car has passed or clearly yields.
Traps that cost marks
Thinking that 'I was here first' beats the right-hand rule; assuming an indicating vehicle has priority; entering a roundabout without looking left for circulating traffic; forgetting that a left turn yields to oncoming vehicles; failing to give way to pedestrians at a zebra crossing.