Supervising a beginner in traffic Let's say you persuade some significant other to ride with you in the city. You both have good bikes, they are inexperienced, and you are (I am) used to commuting, including in traffic.

How do you prepare the inexperienced rider to ride in traffic, and keep them safe while they learn and practice? How do you instruct them while riding?
I ride behind: she sets the pace, concentrates on the road ahead. Being behind I can watch, control the distance between us, speak advice, and manage (i.e. observe and give hand signals to) any vehicles approaching us from behind.



Edit: I just found a quote on the front page of The VEHICULAR CYCLIST (December 2011)


  "I’ve taken three cycling courses since becoming a community officer with the Ottawa Police Service and am on schedule to become a cycling instructor this fall. At the end of every course, I’m absolutely amazed at all the bad habits that I had taught myself throughout the years, ...".


http://www.toronto.ca/cycling/safety/index.htm mentions "CAN-BIKE" courses. One idea might be to take that kind of lesson: I'd at least see how they teach it.