Road markings give instructions before the junction or roundabout arrives. If you read them late, you often end up changing lanes under pressure.
Look well ahead for arrows, destination markings, lane dividers, bus lanes, box junctions, and give-way lines. Each one tells you something about what is expected next.
When you are unsure, hold a safe position, avoid sudden lane changes, and follow signs and markings calmly. A missed turn is safer than a rushed correction.