There are no rules:You can find relevant links as follows:
-Anyone can participate, be it to draw for 20 minutes or the full day .
-Any level of ability is welcome from veteran artists to first time sketchers.
-Any age! Try it with your kids!
- The Sketchcrawl website
- how to participate
- suggested materials
- The Sketchcrawl Forum
- This is the forum for the 20th Sketchcrawl - there are lots and lots of different places participating - just find the one that it local to you.
- This is the map produced for the London Sketchcrawl with suggested venues
Do take a look at Charley Parker's really nice write-up of the Sketchcrawl movement in Sketchcrawl 20.