Mind you don't leave anything in the car, not even for a moment, and not just things of value. A radio, a plastic bag, an old rucksack can all encourage an invisible hand to break the window to get them. While the loss may be small, the broken window would be trouble enough. This applies not only to Warsaw: I have met some German tourists who were robbed of all their possessions, including passports, left in their car in a car park in Gdansk while they just went sightseeing. And the same happened to my neighbour in Lancut in the south of Poland. So take care!
And of course don't leave the car unlocked, not for a second. You never know who may be watching.
I know that in some countries crossing the street against the red light is not a crime. If there is nothing coming, you can just walk on without stopping. Not so in Warsaw or other Polish cities. No matter how safe crossing the street may seem to you, you must stop and wait for the light to change. You may of course be lucky and reach the other side of the street safely but if the police or city guards spot you, you will be in for trouble and may have to pay a fine. You can also be fined for crossing the street at a place other than a zebra crossing. It may be worth your while to take a slight detour rather than get into the guards' hands or... under a passing car.
The Warsaw Avenues are so large and so long that some drivers believe to be on a speedway... Watch out when crossing!!!
During or after a rain do not walk/stay close to the roads, otherwise you have good chance to take a free shower from an urban wave as I did not enjoyed ;-(
Watch yourself as you cross the street.
Jay walking is not against the law but when I say that polish drivers don’t take much notice of pedestrians when they use proper crossing points, you may understand that jay walking is not advisable. Polish drivers tend to drive faster than the speed limit and the often heard squeal of brakes usually means that they have not noticed someone crossing the road again (although I did not actually see any accidents while I was there). If you have a choice and have to cross a busy road, if there is a pedestrian crossing with traffic lights controlling the flow of cars, use them. It is definitely safer than at any other point.
If you have to use a pedestrian crossing where there are no traffic lights, you have to wait for a break in the traffic on your side of the road. Start crossing and the motorists on the opposite lane SHOULD stop for you but make sure that they do before crossing the middle of the road! Good luck……