Avoid Crowds and Crowded Areas:   For instance, we use the Museum Pass for quick, easy entrance into museums.   It helps to avoid mingling with large crowds waiting to get into an attraction or museum.

Take the Bus, Not the Metro:   To me, it seems like it would be easier to get off a bus in an emergency situation rather than trying to get out of a metro station, or even worse, between metro stations.

Plan an Escape BEFORE an Emergency:   I always investigate hotel emergency exits upon check-in.  I try to pick restaurants with an alternate way out, just not a single entrance/exit way.

Check in Early and Travel Light:   I understand at least one of the bombs in Brussels was detonated in a crowded waiting area near a check-in counter at the airport.   I always check in using my phone the night before and I carry on my bags.  I don't like waiting at airline counters with large, stagnant crowds.

Be Aware:  See an unattended bag?  Get away and say something to a police officer or safety official.  See a demonstration or protest?  Walk away.  

Carry Trip Interruption Insurance:  With the right insurance, you can get out of a country more quickly in case of certain emergency situations.

Always Carry at least a Passport COPY:  Write on it your name, medical conditions, hotel you are staying at, contact info at home. Carry a city map too.

And if There is an Emergency Situation:  Try your best NOT to panic and for God's sake, help your fellow man.

Please share your safety tips with me in the comments section below.