Be sure to bring your passport and have a return or onward ticket out of Croatia already booked prior to travel. A U.S. passport allows American citizens to stay up to 90 days without a visa.
Decide on a route. Many trains connect Budapest, Hungary, and Zagreb, Croatia. The Adriatica goes to Rijeka and the Maestral goes to Split. Because of Croatia's boomerang shape, trips will take between 6 and 16 hours. Popular Dubrovnik cannot be reached by train.
Take enough Hungarian forints to pay for the tickets, because credit will probably not be accepted. A first-class train ticket to Croatia can cost anywhere from 4,000 forints to 12,000 forints, depending on the route.
Decide when you'd like to leave. Timetables can be found online at the official Hungarian railway Web site, Elvira (see Resources). Depending on which city you'd like to visit, frequency and duration will differ greatly.
Decide on first-class or second-class travel. Notice that some trains have only second-class seating available. If given the choice, consider that travel guides often recommend first-class seating for travelers.
Go to the local train station or the central ticket office in Budapest. (Train travel to Croatia will most likely depart from the capital.) The central ticket office may be more accommodating to foreigners.
Clarify every detail when booking the ticket. Being specific lessens the high risk of miscommunication for non-native speakers.
