Weaving

Weaving and braking without cause is a good sign that the driver is doing something else.
Candidates are mobile phones, SatNavs, Food.
This chap was leaning forward to enter something on a device stuck to the winscreen.
YouTube

Lane Discipline

Another simple set of rules. Mirror, signal and then manoeuvre.
On the other hand you could just pull out regardless - No mirror, no signal, just pull out.
Watch the video.
HD Video
YouTube

Roundabout Etiquette

It is pretty simple. Look and give way to the vehicle coming from the right. For some it is not simple. THey assume that if the vehicle ahead drives onto the roundabout it is OK for them.
Watch the video:
HD version
YouTube