The night before (or the moment it happens)

Change every clock that doesn't update itselfMixing up meeting times or train times the next morning is the classic slip-up — oven, microwave, car dashboard, wall clocks.
Test every smoke and CO alarmThe American Red Cross encourages everyone to test their smoke alarms as they turn their clocks back to make sure the devices are working. Working smoke alarms cut the risk of dying in a home fire in half as you only have about two minutes to safely get out.
Replace alarm batteries now, don't wait for the chirpFire officials are reminding the public to change the battery in household smoke alarms when residents turn back their clocks.
Check the age on each alarm if conditionalMost smoke alarms should be replaced every 7 to 10 years, and today's smoke and carbon monoxide alarms have the manufacturing date printed on the back of the device so you can check without guessing.
Walk the house and confirm alarm placementPlace a smoke alarm on every level of your home, including the basement, in every bedroom and outside each sleeping area.

Getting your routine ready for darker evenings

Plan your commute home differently for the first week if if you walk cycle drive to workThe first week after daylight saving ends can be a hard adjustment, but anticipating earlier darkness in the evening helps proactively manage the risk on your commute.
Swap dark coats for something brighter or add reflective bitsBundling up in winter coats, which are typically darker colours, makes you harder to see during evening commutes, especially in inclement weather.
Build in extra travel time after darkJourneys that take ten minutes in daylight can take noticeably longer once you're navigating unlit roads, so don't rush.
Get outside in daylight as early in the day as you canThe earlier light exposure helps your body clock adjust and is one of the simple things that can help regulate and restore disrupted circadian rhythms caused by the lack of natural light.
Get a SAD lamp sorted now if you've needed one before if conditionalFor people with seasonal affective disorder, light therapy can help mitigate symptoms like feelings of sadness, decreased energy, and changes in sleep patterns and mood, and it's worth setting up before the lowest-light weeks hit, not after.

Check your headlight aim and bulbs are both workingEnsuring your headlights are properly aimed avoids blinding other drivers and enhances your own visibility on the road. A misaimed or dim headlight is a problem you only notice once it's already dark.
Clean your windscreen inside and outGlare from oncoming headlights and low sun is much worse through a smeared windscreen.
Slow down and expect pedestrians you didn't see yesterdayThe loss of one hour of light in the evenings lines up with when road collision risks are typically the highest, and pedestrians and cyclists are far harder to spot in low light, particularly in dark clothing on unlit roads.
Dip your headlights promptly for oncoming trafficKeep fog lights for actual fog, not as a second pair of headlights.
Watch school routes and bus stops in the early evening if if you drive near schoolsSlow down near schools, bus stops and residential streets in the early evening, when children and commuters are still moving around but the light has already gone.

Put reflective strips or a light on school bags and bikes if if your child walks or cycles to schoolOnce afternoons go dark, a normal coat isn't enough to be seen at a crossing.
Check bike lights actually work, not just that they're fittedA dead bike light gives you zero visibility exactly when you need it most.
Walk your usual route once after dark before you rely on itKerbs, potholes, and unlit stretches look completely different at night than they did in daylight last week.

Put outside lights on a timer so they come on before you get homeA dark house at 5pm is both unsafe to walk into and a signal to anyone casing the street that no one's in.
Check hallway and stair lighting worksThe first dark evening is when you discover the landing bulb's been out for weeks.
Move torches or phone flashlights somewhere you can actually find themSmall thing, but worth doing before, not during, the first power cut of the season.