Not really about how to maintain your bike, more about buying the right one in the first place and buying the right spares.  I’ll be updating this occasionally.

1.The Chain indication.  The first thing manufacturers economise on when building a bike is the chain, and some chains are so cheap that they wear out in three months. I've just had to replace the chainset, chain and cassette on a bike, because the chain had stretched so much in a year, even though the owner had lubricated it properly, and I've had to do that quite a few times. In all the cases, the chain has been a KMC Z51, which is bright and shiny, but is apparently made of cheese. IMO these chains aren't fit for purpose, but as the chap who wore out his in 3 months found, the bike shops won't replace them under warranty. If you're considering buying a new bike, ask what the chain is, and if they say it's a KMC Z51, insist that it's changed for something better, or better still don't buy it as it is likely the rest of it will be cheap and nasty too.

 2. Buying spare parts.  Unless you are familiar with the massive variety of types of bike equipment, it’s probably best not to buy cheap parts and then call in a mechanic to fit them.  I’ve had quite a few instances of being requested to fit something the customer has bought, and it is almost always the wrong part.  The latest was someone who had bought a flash new rear derailleur for his 8 speed bike, only to find out that it would only work on an 11 speed system, so he had wasted about £50.   I’ve also had people ask me to fit new parts to cure a problem that is nothing to do with the part, so again, they’ve wasted their money.  Better to get the mechanic to diagnose the problem, and then supply and fit the necessary parts, it’s cheaper in the long run.

3. Buying mail order bikes.  This can be a cheap way of buying a reasonable bike, but it can also be a disaster, and you can end up with a poor quality bike that needs constant repair.  It if is too good to be true, it probably is, and I would recommend buying a bike from your local dealer, who will be more likely to give you good service and a reliable bike, as they don't want to sell bikes that need repairing all the time.  The other thing to beware of is that the bike will arrive in a box and require some assembly, and unless you are mechanically minded, things can go wrong.  I had a bike a few days ago with the forks facing backwards, and the brake levers so low that the child couldn't reach them and the brake pads mostly missing the rims.  His mother had called me in because she was concerned about how her husband had assembled the bike.  I've also been called in to fix the problem of the right hand pedal being screwed into the left hand crank and vice versa, which can be expensive if the cranks are damaged and need replacing.