As kids fixing your bike was part of the routine but adults generally don’t have the specific tools, time or patience to be a bicycle mechanic; but it’s a no-brainer to keep a new bike, or one already in excellent condition, running perfectly.  
The absence of internal combustion eliminates any mystery and the most important task is keeping the bike clean. Road bikes don’t generally get dirty so it’s an easy job. Wiping the frame and parts off after each and every ride primarily serves as a check that everything bolted on looks right and is still tight.  The turn of a wrench to tighten a loose part prevents a disaster waiting to happen.
As complex as today’s bikes may appear, what you are looking at is all there is.  While moving parts operate independently, each depends upon the system working as a whole.  Accumulated neglect degrades this symbiotic relationship to a point of no return.  The bike still goes, but the equipment works less and less smoothly and can not be brought back, at least not for less than the price of a new bike.
That’s spending stupid money as old faithful still won’t run anywhere near as well as a new bike.  Unlike industries that certify equipment in the interests of commerce and safety, bike shops fix anything on wheels that threatens to move.  Ski shops for example are not allowed to work on bindings past a certain age even if they’re in new condition.
Since poor people are a big constituency the bike industry doesn’t set costly standards and it’s up to each rider to develop a respect for the equipment that begins with the before and after ride inspection.  If something is not as it was, the good news is it’s recent.  If you’re not sure how to fix it or don’t have the right tool don’t fake it. Take it to a bike shop where the fix is almost always quick and cheap.
It’s a great idea to cultivate a relationship with a local shop that doesn’t make a big deal out of these quick fixes.  Most shops don’t have room to store bikes so getting your bike in and out works for everyone.  
The stationary parts hung on the frame are totally overbuilt for the use intended and will remain that way for generations.  The only challenged components are the wheels and failure there is almost always due to rider error.  Spin them after every ride and if they don’t run true know enough not to ride them until made right at your friendly neighborhood bike shop.
Maintaining proper tire pressure and lubricating the drive chain are the only routine maintenance issues a rider faces.  In dry weather every other ride is good enough for the chain. Just lean the bike against something secure and rotate the pedals slowly backwards passing the chain a few times through a rag to remove accumulated grit and then use the same technique for applying lubricant.
Oil is passé as it’s a grime magnet.  The best way is a wax based lubricant that goes on wet but dries quickly. This stuff is advertised as self-cleaning and remarkably it almost is.  It sheds a lot of grit, remains dry and ends the curse of chains that cultivate the filthiest oil known to humankind and magically deposit it on everything it comes close to.  
The chain and rear cluster are mates and when the chain stretches beyond the limits defined by a tool that every bike shop has, both should be replaced.  That’s generally after several thousand miles of riding.  It’s not an expense to be put off even though the chain and cluster will continue to work for thousands of miles beyond their useful life.  Any hard or sudden effort on a worn drive train results in skipping and that can lead to disaster.
Pumping tires isn’t quite as straightforward as it sounds but is a crucial part of any riding routine. Think of it as doing a few reps on a weight machine and a warm up to the ride.  A floor pump with a gage and a head that seamlessly accepts both styles of valves is the tool of choice.  
Before pumping make sure the bike is stable and rotate the wheels so the valve stems are at 6 o’clock.  Only presta valves that have to be unscrewed to allow air in are strong enough to withstand high pressure. Most road tires accept 100 plus pounds of pressure and should be ridden at maximum pressure. Be prepared to concentrate for a short, sweet, full body workout.   
Most people don’t ride in the rain but for those that get caught in it there’s no need to do more than wipe it down and re-lubricate the chain. Most bearings are sealed and everything else is well protected.  There’s no need to lubricate any other parts as long as it’s taken periodically to a shop for inspection and tuning.  
It’s frustrating to see people riding derelict bikes that diminish the experience dramatically. Especially when riding a bike that works as well as new is nothing more than a watchful eye and keeping the thing clean.