Taking bicycles in trains in the EU is generally an easy thing, since there is a regulation that obligates member states to provide this service. However it is not a simple matter, since this service is not equally, readily available in all EU countries. And this goes double for non EU countries.

 One main tip for taking a bicycle in the train, I can give is: always have some bungee cords or ropes to secure the bicycle so it does not move easily. Perhaps a good option that I've seen from bicycle riders in Germany is to have one of those long steel wires with a lock. This will both secure the bike from moving, but also from stealing. Though, I think one can chew off those wires easily, thus I would not put much trust in them in relation to theft in a train in e.g. Eastern Europe, or on a street.