Don't get it wet! This causes electrolysis/corrosion. The number 1 cause of a MacBook not starting. But it can be repaired.
Don't drop it! This causes fractures which are difficult to find.
Don't let it overheat! This causes components to fail. If you cover the air vents or there is fluff buildup inside it can easily overheat. You will hear the fans going full speed trying to cool down. The remedy is keep the insides spotless clean to give it the best chance of cooling itself. The best way to clean is have a professional disassemble the MacBook and give the entire machine an ultrasonic clean. Clean at least once every 3 years and more frequently if it is used in smokey or dusty environments.
Don't operate your MacBook with missing rubber feet! If you do there is a wide gaping hole just 3 mm away from the logic board and a glass of water about to spill across the desk and up this hole that is about to cost you hundreds of dollars in corrosion repair.
If you spill anything on your MacBook you need to act quickly as this will save money. Dont charge it. Dont use it. Dont dry it and forget rice. Get it to someone who can disconnect the battery and check for and remove the liquid.