There are four ways to get around Belgrade, Serbia: GSP buses, private buses, Beovoz (subway) and taxis. Public transport routes are chaotic at times and this may complicate your journey.
The fares on Belgrade's mass transit system vary. At the time of writing, the fare for a journey on both kinds of buses was five dinars 1. The fare for using the Beovoz was also five dinars. Using the taxi will cost you about 2.5 dinars for the beginning of the ride, and a bit more per kilometre.
The Beovoz is more like a train than a real subway. There are only three lines which connect some suburban districts to the downtown area. You can go to Panchevo, the largest town nearest to Belgrade, by using the Beovoz system. Other lines will get you to Batajnica and Rakovica. Unfortunately, there is only one station downtown.
There are about ten taxi companies in Belgrade and their fares are almost similar. You shouldn't pay more than 50 - 75 dinars for a ride, because there is no distance in Belgrade longer than 25km. If you think that you have been ripped off, ask for a receipt for the exact amount you have paid, and then ask your hotel to phone the taxi company on your behalf to check the price. Try to avoid getting a taxi from in front of the main rail station, as many people experience trouble with drivers here who don't want to turn their meters on. If this happens to you, then insist that they start the meter. If this fails, get out of the cab. In general, it is recommended to ask how much a fare will be before you sit in a taxi.
In the evening and throughout the night, fares increase by about 30%. Rides out of the city are double the standard fare during these hours.
If a taxi has a big numbered sign on its roof like 7, 23 or something, it means it is a line taxi. These taxis follow the same route as the buses. The fare is about five to ten dinars, regardless of the distance you travel. However, you won't be the only passenger - line taxis will drive really slowly until four passengers are on board. When these taxis are full, this kind of transport is really efficient.
There are two kinds of buses: state run and privately owned. GSP buses belong to a state run company and GSP also owns the tramways and trolley buses. The company is run badly, so only a small number of vehicles trundle out of the depots. The trams are usually the most efficient way to travel around, but they rarely operate in the winter months. Trolley buses are very uncomfortable, but they cover some important routes.
The other kind of buses are private. Some private companies bought old city buses from western European countries and brought them to Belgrade. All the companies operate a flat fare system which means that everyone pays the same amount regardless of how far they are travelling. The lines function from 4am to midnight.
There is a night service between midnight and 4am, but only some lines function. Buses (and tramways) leave at 00.10, 1.10, 2.10 and 3.10. Under this service, fares are 40% higher (five dinars at the time of writing) than they are during the day.
The best way to solve your problems about lines is to buy a city map. The best map is called Plan grada and costs ten - 15 dinars.