Not too long ago I found myself at the Ronald Reagan airport in Washington, DC with plans to connect with friends in Alexandria, Virginia. One of my friends had e-mailed me earlier in the morning to let me know that Alexandria was two stops away from the airport on the blue line of the Metro, Washington DC's subway system.
After collecting my luggage at the airport, I proceeded to the airport Metro stop and purchased my transfer ticket. When I ascended the escalator to the subway platform for the blue line, I noticed several people standing on the track heading one way and no one standing on the opposite side. I stood with the other people on the platform and entered the subway when the doors opened.
After three stops, I realized that I might have started out in the wrong direction. That realization was confirmed when I arrived at the fourth stop. At that point I located a map on the wall of the train and began to orient myself. A guy in a suit asked, "Where are you headed?"
When I replied, "Alexandria," he simply said, "Oh." Then he followed with the directions I needed to transfer to the correct subway line heading past the airport and on to Alexandria. "Whatever you do," he said, "Don't take the green line."
I followed his directions and successfully disembarked at the Alexandria Metro stop. Since then I have returned to Alexandria several times without any problems.
What I learned from my experience is that it is best to avoid making assumptions. What may look like the right direction, judging from the actions of others, does not always end as you might expect. Take the time to learn what you need to do instead of making assumptions. You'll end up in the right place - most of the time.