Tyres monthly, fluids fortnightly, lights whenever somebody can help you, and never ignore a warning light because the car still drives.
A small number of five-minute checks catch almost everything that turns into an expensive repair or an MOT failure. None of them need tools and all of them can be done on a driveway.
What it covers
Every tip in maintenance
Tyre pressures and tread, oil level, coolant level, screenwash, and all the lights. Together they take five minutes and prevent most roadside breakdowns.
Red means stop as soon as it is safe to do so. Amber means get it looked at soon. Ignoring a red oil pressure or temperature light for a few miles can destroy an engine.
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.
Drive it far enough to charge properly, keep the terminals clean, and use a trickle charger if it sits unused. Short journeys are what kill batteries.
Check every bulb, the wipers, the screenwash, the tyres, the horn and the number plate. A large share of MOT failures are for things that take ten minutes to fix at home.
Fill the tank, inflate the tyres slightly above normal, connect a trickle charger and do not apply the handbrake if it will be months.
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.