How will the food be?
In general, it is always good to stock up on snacks before you board a train. There are exceptions, of course, but food and trains do not usually a happy marriage make. You will have an adventure, however, on board the likes of the Trans-Mongolian Express, where the buffet cars change according to the country you are in: Russia, Mongolia and China. So, lunch is chicken or meat borsht in Russia, with vodka flowing freely, rice and mutton in Mongolia, and a proverbial Chinese cacophony once you cross that border.