This piece for Malachain collects the advice that holds up in practice.
Most breakdowns in older cars come from a short list of neglected items: tyre pressure, oil level, coolant, brake fluid and the battery. A ten-minute check once a month under good light catches almost all of them. Keep a small notebook in the glovebox with dates and mileage so you notice when something starts to need topping up more often.
Change the oil and filter at the interval in the handbook rather than when a light comes on, replace wiper blades every year, and have the brakes inspected when the tyres are rotated. These small costs are far below the price of a single roadside recovery, and a car that is looked after this way often runs comfortably past two hundred thousand kilometres.
The most useful step is usually the first one. Pick a single suggestion, try it for a couple of weeks, and then decide whether it is worth keeping. Small, steady improvements last longer than ambitious plans that are hard to maintain once everyday life gets busy again.
It also helps to talk the subject through with friends or colleagues who have tried something similar. Their experience points out the details that guides leave out: how long things really take, which costs were unexpected, and which shortcuts turned out to be a mistake.
There is more to learn on this subject, and the linked website goes into greater depth. Treat this article as an introduction rather than the final word, and check any important decision against up-to-date, reliable sources before relying on it.