Wood furniture lasts decades if you leave it alone and decades less if you clean it wrong. This is most of what you need to know.
Everyday cleaning
A dry or barely damp cloth, wiped with the grain. That is it. Wring the cloth until it feels almost dry, because standing water is what damages a finish. Dry it off afterwards rather than letting it air dry.
What not to use
Avoid all purpose sprays, anything with ammonia or bleach, and abrasive pads. They strip finish. Silicone based polishes build up a film that attracts dust and makes later refinishing difficult, so skip those too. If you want to polish, a proper wax two or three times a year is plenty.
Heat, water and sunlight
Use a coaster and a mat. A hot mug leaves a white ring in the finish, not the wood, and it happens faster than you would expect. Direct sunlight will fade and dry a wood top over months, so if the desk sits under a window, angle it away or use a blind during the brightest part of the day.
Humidity
Wood moves with the seasons. In a very dry heated room over winter, solid wood can shrink and open small gaps at joints. This is normal and usually closes again in summer. Keeping a room between roughly 40 and 60 percent humidity is kinder to furniture, and to you.
Scratches and dents
Light surface scratches in a finish can often be reduced with a matching wax stick. A dent in solid wood, where the fibres are compressed rather than removed, will sometimes lift with a damp cloth and a warm iron held briefly above it. Test anywhere you try this somewhere hidden first.
Engineered wood
Melamine and laminate tops are more forgiving of spills and less forgiving of deep scratches, because there is no solid wood underneath to sand back. Treat the surface gently and it will look new for years. Do not let water sit at an exposed edge, which is where these tops fail first.
Tighten the bolts
Once a year, check the fixings on any flat packed desk or shelf. They loosen slightly with use, and a wobbly desk is almost always a loose bolt rather than a design fault.