Quora recently had a few pilots respond to questions regarding what pilots watch for when they are flying in the main cabin and their responses were surprising.
Delays
Everyone gets frustrated when delays are as simple as "computer piece" or "waiting for an answer" but sometimes the issue is more complicated than they wish to explain. Airlines should give clear explanations within a reasonable time but they usually don't. If a reason is given, these pilots try to read into it a bit more to have an idea of what is going on or ways that they can describe issues on their flights.
Ice build up
Ice and snow are removed from the plain if it will be an issue and all planes are built with a protective coating to help prevent the build up while in the air but sometimes it still accumulates in the windows. This isn't a worry but can mean that the engine is idling while preparing to land as the engines aren't giving off as much heat as they were. In turn, this can mean that a smooth landing it going to be a bit more difficult.
Speed and Angle
Everything on a flight is timed precisely and normally is only changed if something comes up (turbulence for example) when it is unsafe to proceed as normal. When you feel the plane slow, "level off", this normally is when it is starting it's decent and the pilots start their check list. Be prepared for the seat belt sign to come on since you are in the home stretch. If there is a change in angle on the plane that usually means that the pilot is changing course.
Weird smells
Usually there is not much smelt on planes unless you are beside someone with an upset stomach or a baby but if smells start to come up, the pilots noses go into over drive as things like engine or hydraulic fluid leaks are pretty distinctive. You also of course never want to smell smoke...
Safety
Every plane is different so make sure you know where the emergency exits are and read the emergency cards located in the back of the seat pockets. Some planes have different bracing requirements during emergency landings so make sure you read and are prepared since you won't have time if there is an emergency.
Bonus fact: turbulence is not something that will cause an accident or is a factor to safety
