Sometimes even a check of the departure info doesn't always
help unless the information has been updated timely.

I was at DTW last week with a 4.5 hour layover on a flight to
SAT. Already walked both terminals 2x, did supper and purchased
a magazine to pass time.

Started camping out at the departure gate 2 hours prior given
there was a view of aircraft landing when I overhear the GA
in attendance speaking with a wheelchair bound pax about how
the flight to SAT will be delayed. Upon further inquiry I discover
departure delayed from 7:50pm to 9:30pm due to a late inbound.

Departure monitors were not updated for quite sometime after
I obtained this information.

I find, if you can, it beneficial sometimes to camp out at the
departure gate and keep your ears / eyes open for information.