Having your headlights on seems obvious, but it’s not as simple as that. According to the Highway Code, sidelights and rear registration plate lights should also be lit when driving in the dark. It’s not just useful to do this in the dark though, you’ll want extra visibility in rain and fog, too.
It’s also worth keeping a torch and high-vis clothing in your car, just in case you break down in the dark – it’s important to stay safe and visible.