I usualy indicate when passing parked cars, was told to for my driving test, but I've recently passed my ROSPA test (Gold) and they teach you not to indicte and that the car moving over itslf is enough of an indication.
My pet hate drives me up the wall every day.
Slip road etiquette;
The driver on the main carriageway is in no way obliged to pull out and let traffic from the slip road on, coming from the slip road onto the main carriageway the white line crossed is a give way line.
Now I try to be courtous and pull over when I can, usually this ends up in the other driver speeding up and undertaking or just sitting at the same speed, forcing me to speed up or slow down. If I can't pull over usually people just drift out with no thought as if it's their right to pull out in front, best case they notice just as they are pulling out and slam on the brakes making it worse, instead of speeding up to join at the same speed as the flow of traffic.
Of course not everyone is like this but I see it every day on my commute to work.
Note- Dual carriageway; there aren't many 3 lane stretches in Scotland.