As an American foreign exchange student in Paris, “disappearing into the crowd” was the first lesson to master, said Bay State native Kaila Dwinell.

Now 26, she was a foreign exchange student at Institut Catholique de Paris for a year in 2011 to 2012. Here’s her advice for keeping safe overseas after yesterday’s unprovoked acid attack on four Boston College students by an alleged mentally disturbed woman as they were boarding a train in Marseille:

The first night in Paris I realized I had to distance myself from Americans who were gaudy or excessively loud. We were going to live in the city for a year and I could hear the French talking about us.

You need to blend in. It’s a skill to be able to disappear into the crowd when you have to. I’d wear a black hoodie and pull it up over my head when I sensed danger. Also wear sensible shoes and be prepared to run.

But first you must understand the language and the culture so you can try to fit in. I’m fluent in French and quickly picked up the slang, too. That makes a huge difference. It allows you to have a conversation.

I could listen to what the French people were saying. They knew some of us were Americans.

Once I was followed home from school block after block by this strange guy. I went into a grocery store where they knew me and I yelled in French “Sa Sussit!” (That’s enough.) I added “Arrete de me suvre” (Stop following me). He quickly left.

On my first night in Paris, I walked in the wrong direction and couldn’t get a cab. I asked a middle-aged French woman for help and she pulled a cab over in seconds. She just stepped in front of everyone and hailed it down. She then turned to the others around her and yelled at them for cutting me off. It also taught me to learn where the bad neighborhoods are.

You just need to realize you’re not home anymore. Put your earbuds in your pocket and soak in the sounds of your surroundings.

But violence can be so random and unavoidable. Paris to Marseille is such an easy trip. A lot of the trouble from the outskirts of Paris just moved down to Marseille. And train stations are a gathering point for all kinds of people.

No matter how careful you are, terrible things can happen to young Americans living abroad in these difficult times. My advice is to just stay calm, stay aware.