When looking for parking in the city you usually search for obviously marked parking spaces or at least for street signs that don't allow you to park in a zone. Some parking zones can restrict parking to specific vehicle types, for example, commercial trucks in a delivery route. Or limit the total time you can stay parked, for example, to 20 minutes. Or even they can restrict the parking in the zone during some scheduled during the day, for example, only 9 am to 4 pm. Or limit parking to specific days of the week, for example, allowing to park only during weekends.
Some streets in the city centers also have a cleaning schedule where street parking is not allowed on one side of the street to allow the cleaning machine and workers to mechanically brush and sweep the road. This schedule is usually available online for citizens to check in advance. But also marked in signposts at every corner in the street. If you don't remove your car during street cleaning time, your car will be fined or even towed if it obstructs the movement of the cleaning machine.
Other traffic signs to look for illegally parked areas are curb stripping, color codes, and other pavements markings. Regulations can change from city to city but there are universally used colors to indicate parking spaces on the curb:
In public zones with paid parking, you need to use a parking meter machine. Different parking meters are used in different cities, but usually, after parking your car you need to pay for the intended minutes you need to park your car and put a printed paper receipt with time and date in a visible area inside your car. Usually the front dashboard.
The newest parking meters don't print paper receipts at all but record your car's license plate. Also, payment can be usually done by credit cards. However, some cities only accept official parking cards with prepaid credits.
Nevertheless, parking zones with parking meters are usually located in the busiest areas of the city center. For that reason, they usually enforce a maximum parking time limit, like 90 minutes. Even if you have paid for more than 90 minutes of parking, your car would be fined or removed after the time limit has passed.
To enforce legal parking and rules, cities often have parking enforcement officers that will patrol the city in search of parking violators. They carry connected handhelds machines to report the violation and print paper fines and notices for the car's owner. These parking tickets are usually attached in the front windshield under a wiper.
To pay for parking fines, cities usually provide web pages with electronic payment systems where you can pay online with a credit card. A more traditional way to pay the parking violations is to go physically to the town hall bursar or traffic office and pay with cash.
Apart from the written traffic law and parking regulations. There is more discussion about what is considered illegal parking or not. While a parking zone can be public or private. Private parking spaces can have a totally different set of rules set by the owners and landlords. For example, there is quite a controversial discussion around double parking being illegal or not. While parking occupying two or more spaces is not strictly illegal by traffic regulation, a landlord would have the right to call for towing your car out of a private parking area.
Legal regulations are sometimes very blurry. So our sincere recommendation for most of the time is to use your common sense and always be civil. Don't do to others what you don't want for yourself. We are confident our world will be a happier and safer place following this basic single rule.