Park where indicated, take care of the environment, buy the local guidebook when possible (this is one of the ways you can help local route setters), clean up your shoes before climbing, don't spray beta, be polite.
Climbing guidebook describes 12 areas of Haute Bretagne, 9 of which are in the (wider) surroundings of Rennes / one area close to the sea / + one bouldering area: Rochers du Blaireau.