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
2. Let's wear appropriate clothes, warm and/or waterproof if necessary.
3. Let's stay well hydrated! Better keep a water bottle near at all times.
4. Let's make sure that our bikes are in good order. Especially, it is important to have all the required reflectors installed (white in the front; red in the back; orange or white in the front wheel; red in the back wheel). Don't forget that cops often use the absence of reflectors to harass cyclists.
5. We're not blocking traffic, we are traffic! The most important is to keep moving and stay united. For basic safety reasons, it is preferable to go in the direction of the traffic. It is also preferable to stop at the red lights when possible, although the physical length of the critical mass sometimes make it necessary for participants to secure street intersections by placing themselves in front of the cars going across, in order to keep the procession well united. Why not take this opportunity to explain to motorists why we're doing this in the first place!?
6. If, for a reason or another, the critical mass is cut in two or more smaller groups, it is always possible to reunite a little bit further, a little bit later. The main tactical advantage of the critical mass, by definition, is the force of numbers! Two large contingents or several smaller contingents taking off in different directions and joining back together can have interesting effects. In any case, let's stay united as much as possible and let's keep our eye on our physical objectives!
7. All routes are optional! Fuck P-6! A protest without spontaneity is like a bicycle without wheels!
8. A critical mass is always more enjoyable and unavoidable if it's audible and visible from afar! Let's dress up our bikes and ourselves! Let's turn our flashers on! Let's bring some bells, whistles and other noisemakers. Let's not forget the classic playing card in the spokes! And let's break out all our best anti-car, anti-capitalist chants!
9. The police is not our friend. Better to keep our interaction with the cops to a bare minimum. This means not befriending them as well as not getting up in their grill for no reason. In other words: we have nothing to tell them, no permission to ask of them, and no apologies to offer them.
10. Smile! Let's have fun!
HAVE A GLORIOUS CRITICAL MASS! HAVE A GOOD ANTI-CAPITALIST SUMMER!
-- Your friendly CLAC hosts
:)