First of all, we suggest you read this fine backgrounder on the history of critical mass :
http://en.wikipedia.org/wiki/Critical_Mass_%28cycling%29
1. Above all, whatever happens, let's stick together and always keep each other's safety in mind! Let's get to either the meeting points in time (as much as possible), in small groups of friends, neighbours, or family members. Let's take care of each other from beginning to end, and let's avoid any unnecessary risks or dangers.