The Big Killers: Death By Stupidity

Not looking before turning on to the road from the sidewalk
Believe it or not, some people routinely start journeys by launching off the pavement into busy roads without checking traffic behind them. I suspect that a lot of these people ride very close to the curb and think that this part of the road will always be safe for them, or that traffic will get out of their way. Sooner or later a car will prove them wrong.

Other people commit this crime without meaning to. They think they've looked, but chose a starting place where they couldn't see the road properly - at least in the fast glance they took - because of a bend, or a tall van placed at the side of the road in a critical spot.

Finally, some people are seduced into not-looking by pavement riding or using a bike path that crosses junctions. They fall into a rhythm and forget to break it when crossing roads at junctions.

Riding against traffic
Let's be fair: sometimes when people do stupid things it's someone else's stupidity that
is at fault. In some parts of America (but nowhere else I've heard of) cyclists are still encouraged to ride facing car traffic, rather than riding with. The theory seems to be that cyclists are more like pedestrians than cars - and this advice is quite good for pedestrians, who can spot especially reckless oncoming horseless carriages and dive out of the way (presumably off cliffs and into rivers, as there was nothing by the side of the road they could walk on

Not riding in a straight line
Drivers need to know where you will be next. So ride predictably, following a path that stays a constant distance from the curb. Even if you see broken glass in front of you, don't swerve unless you know your back is clear.

Riding with a half metre margin between you and the kerb instead skimming will make weaving around glass and potholes easier, by the way - because you will be able to swerve inwards as well as outwards. However, you should still check before swerving inwards if you possibly can - it's always possible that a very stupid cyclist is trying to undertake you their. Still, if you have a choice between definite immediate death and swerving inwards, I'd say that inwards looks good.