Always indicate. Always.
Nothing worse than assholes (on any road, motorway or residential area etc) suddenly slowing down and shifting position while you end up rushing up their ass because they aren't indicating.
Great post except for
"If you are not sure of the speed limit keep up with traffic."
In the UK at least, you can work out the speed of the road you're on within 10 seconds no matter where you are in the country.
Assuming you're in a normal car (not a van or anything):
- does it have regular street lights? It's 30mph
- does it have no/rare street lights? It's 60mph
- even if either of the above are true, does it have blue road signs? It's a motorway, 70mph
Any exception to these three rules will have "repeater" speed limit signs every 25 yards or so.
With this quick rule of thumb, within a few seconds you can work out what speed to go no matter what.