Common sense is an oxymoron. There's no sense that we all have in common. He was asking us to impart our knowledge.

Of course, it depends on your terrain, your bike, and your riding schedule.

Depending on tire size, inflate or check tire pressure every week. If you have very narrow tires, check every day or two.

Less frequently, check chain cleanliness and lubrication.

Overhaul your four main bearings every few years. The four main bearings, if they are serviceable, are 2 hubs, headset, and bottom bracket.

Check cables for free operation every month or two. Same for gear shifting and braking.

Every three to six months, do a safety check: check wheel trueness (truth?), check tightness of axle nuts or skewers, seat binder bolts, stem bolts, handlebar binder bolts, proper brake operation. Check health of tires.