As well as getting information IN (about what's around you), you should give information OUT (about what you intend to do).
Do this by signalling, usually with lights on your car. They could warn others about your intention to …
1. Turn (by flashing AMBER direction indicators), or reposition
2. Slow (by rear RED lights; automatic when using footbrake)
3. Reverse (by rear WHITE lights; auto. when in reverse gear)
4. Be a hazard (by ALL direction indicators flashing AMBER)
5. "Be there" (by horn / flashing headlights, if going unnoticed)