Boiler maintenance is something that should be done without fail as it can be very inconvenient and expensive to repair and service when something major goes wrong. Even if it does not come down to a sputtering halt one day, a boiler that is not running in its optimal working condition will be expensive to run. It will be using a lot of electricity while not heating as well as it should. It also does not mean that boilers are prone to breakdowns. Modern boilers are well made devices that are pretty much foolproof, as long as they are taken care of.
Keep the space where the boiler is fixed clear of clutter, this is the first step in boiler maintenance. Never have anything leaning on the boiler or crowding the room, there should be some air around it. The air around it and the device will get fairly hot during operation so anything that can melt, singe or catch fire should not be near or on it when it is running.
If you do not use the boiler in summer and switch it off during the warm months, you should inspect it before switching it on in winter. If you can, drain out the water before switching it off for a few months. The inspection can happen just before the winter months, just when it is getting cold. Have a look at the boiler, make sure there are no puddles or cracks anywhere. You can also look for sludge or other things that look out of place.
After you switch it on, look for leaks and other signs of malfunctions like steam and other hot water leaks. The inspection is fairly simple and does not require any technical, boiler maintenance expertise, just a good eye.
Apart from these three things, your boiler should be serviced by professionals at least once every 36 months.