Book your ticket with Rail Europe by calling (888) 382-RAIL or going to the Rail Europe Web site (see Resources).
Book second class fares within a few days of travel for comfortable enough economy travel into Belgrade. You may feel a bit cramped, but feeling all that extra dough in your pocket should make up for it!
Reserve sleeper car accommodations for greater security and privacy on evening trains to enjoy free meals, refreshing rest and more room; but book early. These accommodations are limited.
Lug your luggage as far as the Belgrade station, but if you're not staying long, leave it in a locker for 2 euros per day and spare yourself the misery of toting it up the steep hill into Belgrade's city center.
Put it on your plastic and spare yourself the headache of figuring out exchange rates and paying steeper fees to trade your cash.
Guard your travel documents with your life. Losing these could ruin a lot more than just your train ride.
Use taxis for ground transportation within either city only if you've called in advance for fare information or set a price before getting underway.
Choose underground rail to and from the main stations in Prague, as you will save time and money. The Red Line or Metro Line C goes into both Hlavni and Masarykovo stations.
Be certain to board the right train. Once the doors close, you're going to the next city on that train, whether it's yours or not.
Double check the time schedules upon your arrival to the station, as the Belgrade route tends to more frequent delays and switches than other European routes.