SEE notes: Oncoming cage turns left
Vehicles truning left in front of you cause the classic bike accident.
Things to look out for on the cage: turn signals, lane change into turn lane, car hood dips as brakes are applied, car hood rises as car accelerates, wheel turn without deceleration.
Driver danger signs: distraction with object, face turned down towards object on dash or in lap, face turned towards passenger in conversation.
If the car appears to be turning and not stopping, either move to an escape route previously evaluated, change speed, or initiate crash avoidanc/evasion mode.
If the driver is distracted, evaluate his potential to turn across you, and consider additional active conspicuity measures.
Conspicuity moves include riding in a gentle weave pattern or changing sublanes or lanes to the right. See UK DOT (page 15) and Better Motorcycling blog on the subject. The idea is that any rightwards move changes the oncoming driver's angle of view to show more of the bike and rider.
Flashing lights and/or horn might alert an inattentive or distracted driver.
Consider using a vehicle as a shield. But be aware that the shield vehicle may stop. A colleague of ours once took off from a stoplight, with a truck to his left that he was using as a shield. The truck driver saw a red-light-runner coming from his left, and jammed on. Our friend didn't stop as quickly as the shielding truck did, and was taken out by the red light runner. Bear in mind that, even from as little as 10 MPH, your stopping distance is approximately 13.4 feet, if you include reaction time and braking distance. As you probably can't see your shielding vehicle's brake lights, your stopping distance might even be longer. That 13 feet is enough to lose your shield and be in a very dangerous situation.
Crash avoidance/evasion is covered in it's own section.
Changing position or speed might provide additional escape paths.