My experience is probably different to yours, but on the whole I would have to admit I would also avoid railpasses unless you want to be completely loose about your plans. If you have enough of an idea of what you want to see and where you want to go in advance, buying restricted advance purchase tickets makes more sense. It sounds to me that if you are doing three or four countries in one trip, then you'll be basing yourselves in each one in turn (rather than doing the backpacker thing and just going everywhere in one big trip). If this is the case, then being based in a big city will make trips out to other twns and regions easier. The Netherlands is so well served by train that it doesn't matter where you stay; for France you'll find that Paris is the best hub from which to explore the country, because virtually all TGV and long distance routes radiate from there.
For your travels you need to spend some time with these websites. Generally, all European trains open for booking and reservation three months before departure.
Seat61.com - written by an ex-British Rail employee, it's principally designed to help British travellers work out how to get from the UK to anywhere in Europe, rather than from one continental country to another. However the advice and recommendations about routing and trains is very useful.
Nederlandse Spoorwegen Dutch Railways
voyages-sncf.fr - the travel agency of SNCF (French railways). There's an English version, just scroll down the homepage and click on the Union Flag at the bottom left. The place to start when booking trips from France to anywhere in Europe, and to research your routes between NL, FR and ES. The sooner you book, and if you travel off peak, the better deals you'll get. The website will always advise you of the lowest priced ticket available when you search, but if you want to explore some of the current offers, you can have a poke around the (French only) part of the site which lists all the current train promos
here
bahn.de - the website of Deutsche Bahn (German railways) but with a timetable search engine that covers just about every country you could want to go in Europe. To get the English version click on "Internat. Guests" in the red bar at the top right of the homepage.
The Thomas Cook European Railway timetable that was mentionned earlier is published four times a year.
This one is valid until early June, then
this one (pre-order only). If, like me, you love a good map, then they also publish a complete
European map of passenger rail routes.
Happy travels,
*j*