This may be obvious to people, and it’s probably near useless now that everyone has a GPS in their car or on their smartphone; but if you want to turn around and go the opposite direction on the highway, you should take the second exit.  The first exit will likely turn to the right of the highway, while the second one will likely loop over or under the highway and let you go in the other direction.

Of note, the A exit is only first going in one direction, so don’t assume that A always becomes before B.