There are definitely some standard warning signs you can look for:
Any colored fluid or oil-like substance dripping from the wing.
Any colored fluid or oil-like substance dripping from the wing.Any sign of buckling or irregular bends in the skin of the aircraft or popped rivets
Any sign of buckling or irregular bends in the skin of the aircraft or popped rivetsFire, smoke or the smell of something burning
Fire, smoke or the smell of something burningLoose or missing panels or farings
Loose or missing panels or faringsPresence of a red streamer or anything that says "REMOVE BEFORE FLIGHT"
Presence of a red streamer or anything that says "REMOVE BEFORE FLIGHT"When a door is closed and secure for flight it should have an orange strip diagonally across the window; if the strip is hanging straight down, something has gone wrong.
When a door is closed and secure for flight it should have an orange strip diagonally across the window; if the strip is hanging straight down, something has gone wrong.Any member of the flight crew that appears drunk, woozy or disoriented
Any member of the flight crew that appears drunk, woozy or disoriented