Learn to judge available traction
In this discussion so far, I haven't seen much mention of learning to judge available traction. It's not just turning off into dirt, but wet roads, leaves, pavement with sand, dirt or gravel on it, paint on the road, tar snakes.
When I'm riding, I'm always trying to figure out how much traction to expect. I don't trust the traction when riding over paint, cobblestones, bricks, anything wet. I'm probably overly cautious in that area, but that's better than getting surprised by a sudden loss of traction and going down.
I can remember leading a small group ride a few years back where I had one very experienced rider along and one fairly new rider on a Ninja 250. We needed to make a U-turn on a country road, so I stopped the group first, then I turned around, the experienced rider turned around, and the 250 rider didn't really start turning sharply until half way around the turn, and he accelerated too much, so when he went off in the dirt on the other side he hit the front brake and down he went. No injuries to either the rider or the bike, just some dirt and dust on both.
The point is that the new rider didn't really understand how much less traction there was in the dirt on the side (in addition to several other riding errors). I'm not sure how to teach new riders about available traction other than lecturing on the subject and hoping they grasp the concepts and remember it when needed.
__Scott R. Nelson, 2008 KTM 990 Adventure, 2001 Honda XR650L, Folsom, CA