"Remember to look both ways before crossing the street"
Growing up, that is one of those standard parenting phrases that you hear so many times you learn to just nod and say "I know". However, that is very good advice, especially when the cars are coming from a different direction than you are used to. In London, I have been working on remembering to look right, then left, before crossing the street. I didn't realize how accustomed I was to looking left first, until I had the constant visual reminders on the sidewalk that say 'Look Right -> '
Other street signs in London are also different. Where in the US it seems fairly standard for little green signs saying the name of the street to be posted on poles on the street corner, in London the street sign is posted on a building or gate... if it is there at all.
When the street signs are around, at least they are very informative, telling you exactly what section of the city you are in and the postal code, in addition to the street name. Other good signals to recognize are crosswalks marked with black and white poles topped with yellow bulbs:
These crosswalks imply that a vehicle must stop for pedestrians in the crosswalk. That does not mean that a taxi might not beep at you because it is impatient, but at least you will be able to safely cross the street. Also while crossing streets, you may note that the street lights go through a slightly different cycle. First they are green, then yellow, then red, then right before the lights turn green again both the red and the yellow light up. Many corners with stoplights also have the little green and red men to tell you when you are allowed to cross the street, however these are highly irregular, and the green walking man does not stay lit for very long.
I've noticed a few other random differences as well. Instead of a sign saying 'Detour' for a road being closed, it will read 'Diversion'. Speed bumps are referred to as speed humps. Parking meters are located in one spot on the street instead of at every parking space: