You should be able to wipe down and inspect your bike in about ten minutes or less. Look for anything rubbing, clicking, or loose and inspect the frame and wheels for cracking.
You should also do a larger clean after really muddy rides or before major service. The Global Mountain Bike Network has made a video detailing every step in a thirty-minute clean.
1. HEADSETS, HUBS, CRANKS
The headset affects steering. Hubs affect your wheels, and cranks are what turns the chain. These components are vital but easy to overlook. Make sure they are all tight and moving smoothly, and carefully adjust them if not. They also may need to be greased.
Regular maintenance means cleaning and making sure they feel smooth. You may need to do more in-depth work every few years, or after a particularly harsh ride for the bike. It’s not mountain bike specific, but Bikeradar’s article on hub service may be helpful.