Rail
The Serbian rail network covers the main routes but trains are often slow and aging outside the new Belgrade-Novi Sad high-speed line. The train from Belgrade to Nis takes about four hours. For the main corridors, trains are affordable and scenic. For smaller destinations, buses are usually faster and more frequent.
Bus
Buses are the workhorse of Serbian public transport and serve virtually every town and village. Services are frequent on main routes and reasonably comfortable. Buy tickets at the bus station (autobuska stanica) -- there is usually a small platform fee on top of the ticket price. For popular routes, booking a day ahead in summer is wise.
Car
Renting a car gives you the most freedom, especially for reaching monasteries, mountain areas like Zlatibor, and the Djerdap Gorge. Roads between major cities are generally good, though rural roads can be rough. Serbian driving can be aggressive, and overtaking on two-lane roads requires confidence. Fuel is cheaper than in Western Europe.
City transport
Belgrade has an extensive bus and tram network. Buy a BusPlus card at kiosks for cheaper fares, or pay on board. Taxis are cheap -- use the CarGo or Pink Taxi apps rather than hailing on the street. Novi Sad is compact enough to walk.