Critical mass doos and donts?

The OP didn't ask: Can someone tell me whether they CM is a great advert for cycling? They asked for advice on what goes on, how to join in.

I think the worst advert for cycling is people who rise fast on busy London commuter streets. Not a once a month rolling party.

what you mean like 21 mph? because the vehicular traffic dosent go any faster than it did in 1906 needs leaving behind