Train travel Benelux Countries

Non high-speed trains in the region don't allow reservations, all seats are first come first serve. So you can purchase tickets at the station on the day of your journey. Sometimes seating can be scarce during the morning and evening rush hours to/from the larger cities, but for the most part there are lots of seats to go around. High-speed services like the Thalys, and Fyra which do the route from Brussels-Antwerp-Rotterdam-Amsterdam require reservations, and you can only get cheap fares by booking way in advance; 90 days allowed.

Note that Fyra is having technology problems and may not be running on your line. Belgian trains can be very crowded, even more so at rush hour and school rush hours. This is not a slam, but Belgian local trains are a very lived-in, local bedrock institution. One night, a bunch of tipsy (?) teenage (?) girls were having something like an onboard bachelorette party, walking up and down the train with signs around the bride and maid of honor's necks. I can't describe the party any better because that's one of the few times I've met young people in Belgium who didn't speak English. I wouldn't say connections were any worse than anywhere else, but I have missed a few close local connections. And I've seen some very long lines for (human attended) ticket windows in Antwerp and Brussels.

I've never had an experience where I couldn't find a seat on a Belgian train. Even during rush hour on a heavily commuted line like Brussels to Leuven. I had to stand on a Dutch train once for a few minutes during rush hour from Utrecht, but that's it.

I took an early morning train from Bruges to Brussels two years ago, had to stand for the entire journey:( It was filled with commuters, it was not a fun.

Ron,
Where you can, make reservations and travel First Class, it is always worth the extra $, especially on Thalys!

Disagree very much with that last statement. First class is great if you need to accomplish some work en-route, or if you want waiter service (not available on domestic trains in Belgium). But otherwise, it doesn't buy you much additional comfort, and for the short durations of most of the trips, for me, it would be very hard to justify the extra costs, unless my company was footing the bill.

I've never used First Class for the maroon train (Thalys). The large seats with plenty of foot and legroom are plenty for me. For me, upgrading with the extra money to First is gilding the lily - a waste.

I normally only go for first-class on trains rides more than four hours, but Thalys is the exception. Thalys first class gets you free wifi, light snack and beverage. For me it's worth the splurge.