Visitors to Europe often overpay for cross-border and inter-country train tickets, not realising that lesser-known local websites offer discounts to non-residents.

European countries are constantly improving their intercity rail networks and high-speed trains have slashed travel times around the continent. Spain alone has built 3,000km of track for trains travelling at speeds up to 300km/h.

This spring, rail travel will become even more convenient as the Spanish and French rail networks integrate, allowing passengers in one country to travel by high-speed rail to a major city in the other. In mid-April, France’s state-owned rail company SNCF plans to start running high-speed service between Paris and Barcelona, while Spain’s national train operator RENFE has already debuted high-speed service between Barcelona and Madrid. Final details have yet to be announced, but it seems reasonable to predict a travel time between Paris and Madrid of nine hours; driving a similar route would take about 15.

Europe’s other recent high-speed rail revolutions include the April 2012 debut of Italo, a privately-run service that connects Milan, Rome and Naples, and the December 2011 launch of Westbahn, a privately-run train service between Vienna and Salzburg.

But despite the massive popularity of touring Europe by rail, major online travel agencies such as Expedia and Hotwire don’t sell European rail tickets. From a one-way trip to a complex multi-country journey, the broadest options and best-priced tickets can usually only be found on a few regional sites.

Look for single-country discounts
If you’re visiting a major European country and plan to see more than one city within it, you’ll save significantly by booking a single-country pass, which offers foreign travellers hop-on, hop-off use for a specified number of days and are sold by most national railway companies.

Railways often don’t require reservations trains in advance, so the passes allow flexibility for last minute planning. And the rail networks usually let you pay in your own currency, helping you avoid foreign exchange fees. They’ll also mail the tickets to major countries for free.

Say that you and another adult are planning to visit Germany in May, stopping in Cologne, Berlin, Munich, the famous Neuschwanstein Castle (near Füssen) and Frankfurt Airport. According to the offers page of Germany’s state-owned rail operator Deutsche Bahn, non-Europeans can purchase “twin” passes – tickets good for a pair of travellers – for a multi-city itinerary for $371, or about $185 a person. In comparison, a German using the site to book point-to-point tickets would pay 188 euro, or about $250 per adult – which would be about a third more than the pass offered to non-Europeans.

Europeans can instead take advantage of Germany’s national rail card, such as the BahnCard 25, which provides a 25% discount, justifying its 60 euro cost if you spend more than 200 euro a year on train trips. That said, it's rare for a nation to offer such a card.

Most of Europe’s national railways have similar English-language offer websites, including SNCF’s special deals page, RENFE’s Spain Pass page, Italian railway company Trenitalia’s offers page and the website of Britain’s Association of Train Operating Companies, BritRail, in combination with Network Rail Enquiries.

If your itinerary involves travel through more than one country, you may also save by visiting more than one website to buy your tickets. For instance, to travel on a route from London to Nice, you could book a ticket on the Eurostar line between London and Paris and then book your onward journey on the TGV, France’s high-speed rail.

Save by booking direct
Heavily advertised third-party agencies, such as RailEurope.comRailbookers and Raileasy, generally do not offer the best value for travellers. Especially for simple trips, such as a one-way ticket between cities, you’ll typically save by buying online directly from a railway company. But if you’re short of time and don’t have the patience for comparison-shopping, these third-party agencies are reliable and easy to understand.

To illustrate, let’s take a look at the same May itinerary for five German cities. If you were to price the trip through RailEurope, you would easily find the same Deutsche Bahn twin pass for only $466, or $233 a person — 25% more expensive than booking directly. On the other hand, if you hadn’t known to check Deutsche Bahn’s separate “offers” page, the discount would not have appeared as a result. Deutsche Bahn’s main booking tool doesn’t automatically show non-residents the discounted rates they qualify for.

Best sites for timetables
For pricing tickets, Germany’s Deutsche Bahn’s website (and its free DB Navigator app for iPhone, Android and Blackberry devices) has the most comprehensive timetable database for nearly all of Europe. As a downside, the site only lets you book Deutsche Bahn trains and a handful of international trips that originate in Germany; the schedule information for other national lines is for planning purposes only. For help, see author Rick Steves’ tips on using the Deutsche Bahn site and the app.

Another good resource isThe Man in Seat 61, the most comprehensive site for helping travellers plan rail journeys worldwide. The site is so named because its creator, Mark Smith, is a former manager in the rail industry who preferred seat 61 on his Eurostar trips because of its superior first class window view.

To pass, or not to pass?
Many foreign visitors still think of Eurail – a company that sells European rail passes to non-European residents at dramatically discounted rates – as a 1980s activity for young backpackers. But Eurail passes, which allow for nearly unlimited travel between specified countries within a set time period, have matured. Adult first-class options, for example, ensure that the other people in your train car will be similarly grown up. That said, Eurail still offers dramatic discounts on standard-class tickets for people under age 25.

Eurail is continually broadening its coverage area, recently welcoming two more companies to its long roster of train lines. As of 1 January, some Eurail passes, such as the Eurail Select Pass (for travel in up to five countries), are good on Westbahn’s high-speed service between Salzburg and Vienna and on European routes to Istanbul that are operated by TCDD, the Turkish state railway.

But passes aren't always the answer. If you're travelling in Europe for less than 10 days consecutively and not crossing many borders, you're unlikely to get the most value out of a Eurail pass. Instead, you’ll usually find a better bargain booking point-to-point tickets directly with the nation’s railway company.

InterRail is like Eurail for Europeans, and it works much the same way. InterRail passes come in two kinds: a global pass, which covers 30 countries for various lengths of time (the briefest being any five days of travel within a 10-day period), and single-country passes for each of 27 countries (with Belgium, Netherlands and Luxembourg counting as a single “country”). Reservations are only required for international and long-distance trains, though these can often be booked a few hours prior to departure.

Sean O’Neill is the travel tech columnist for BBC Travel