Check pressure cold, monthly, against the figure in the door shut. To change one, loosen the bolts before jacking, use the jacking point in the manual, and re-torque after.
- Check pressures when the tyres are cold, before driving, using the figures on the sticker in the driver's door shut or the fuel flap.
- Include the spare, which is always flat when you need it.
- To change one: handbrake on, in gear, wheel chocked, on level ground.
- Loosen the wheel bolts half a turn before jacking, while the tyre is still on the ground.
- Jack at the manufacturer's jacking point only. Anywhere else buckles the sill.
- Fit the spare, lower it, then tighten in a star pattern and get the torque checked properly as soon as possible.
Never get under a car supported only by a jack. Axle stands exist for this reason and people are killed by this every year. And check whether you have a spare at all: many new cars have only a sealant kit, which does not work for a sidewall cut.
Underinflated tyres wear at the edges, use more fuel and handle badly, and they are responsible for a significant share of blowouts. It is the cheapest safety check there is.
Gas work requires Gas Safe registration by law and most electrical work is notifiable. Where a tip says to call somebody, that is the advice. Full disclaimer.