We (me, wife, two daughters and son in-law) are planning a European adventure. We have been all over France, Italy and the UK. Now we are thinking Netherlands/Germany/Austria/Switzerland and/or others. Fly-in to one city and out another. Take trains between destinations. Nothing fancy for accommodations. But I am at a loss for the destinations. We are really wide open at this time and need suggestions. Any thoughts?
What do you like to do? Museums? Hiking? Scenic cruising? Flowers? That will help determine a plan. A suggestion: start in Amsterdam and end in Munich. Tour the Netherlands from Amsterdam (museums, history, windmills, flowers if you time it right) then head to the Rhine/Mosel rivers in Germany (beautiful scenery, castles). Finish in Munich (museums, palaces, food).
What time of year?
Costs in Switzerland are likely to be much higher than in the other countries you mentioned.
Possibilities are nearly infinite, so you need to tell us something about your interests.
September is our preferred time to travel. Hiking, museums, food, beer, wine, palaces all work for us. No flowers or high end dining.
All are good. Just looking at a map (and not knowing what your preferred pace is): Amsterdam (with day trips), Berlin, Dresden (optional), Munich, Salzburg, Vienna. Or A'dam, Berlin, Dresden (still optional), Prague, Vienna, possibly tagging on Budapest at the end (better wine) if you are fast-paced. Switzerland's an outlier.
Time to start reading and watching.
Go to your local library and take out as many books, from as many different companies, as you can on your possible destinations. See if any places call to you now.
Watch as many travel videos as you can; Rick's are here, when you scroll down: https://www.ricksteves.com/watch-read-listen/video/tv-show. Also look on YouTube. Again, you may spot something that says "come to me."
Read trip reports, not only on this Forum, but also on others like Fodors http://www.fodors.com/community/europe/tripreport.cfm and Trip Advisor https://www.tripadvisor.com/ListForums-g4-i11-Europe.html.
Ask your friends where they've been recently. You may learn about a place you hadn't thought of.
Any bucket list places that anyone in your group has? Plan a trip around these.
Note that September is supposed to be the best month for the Alps, weather-wise. So, Switzerland makes good sense at that time of year. My one trip to Switzerland was in September 2014, and had great weather in the Berner Oberland. However, my walking tour guide in Lausanne had just been to Zermatt while I was in the Berner Oberland, and the Matterhorn was fogged in for almost all of the 3 days she was there. So, no guarantees.
"...at a loss for the destinations." You basically have a choice in that regard, do the usual tourist thing by hitting the cities/sights done by tourists, ie, your entire itinerary consists of tourist places, or choose places fitting to your interests, priorities instead of following guide book itineraries. Most people have the same interests in seeking out which cities/towns to visit.
On Germany and Austria I heartily recommend Berlin and Vienna on one's first trip in those countries. My first trip to Europe I made sure to include (West) Berlin and Vienna, bottom line is what do you want to see as regards to museums, places, etc. Look at Rough Guide Germany and for Austria.
We had been to much of Italy, England, Wales, Scotland, and Paris (no not anywhere else to speak of in France). My husband had blitzed central Europe in his twenties. Last summer we added or saw in more depth, The Netherlands, Germany, The Czech Republic, and Austria. This is highly personal, but I would see Amsterdam, Prague, and Vienna . After those three I'd add either a few German cities, Budapest, or both. I suspect there are people who will think I'm crazy not to emphasize Germany and Switzerland, which we sampled. But it is all very personal.
I suggest the Eyewitness Guides as a chposing, but not planning resource.
A couple of ways you can use this web site: Under the link for Explore Europe, see the At a Glance section for each country, such as the Netherlands, to get an idea of what Rick's books will cover. Sites are "star" rated on that list, as well as the Plan link will give more timing advice within one country.
None of our guided tours quite fit your route, but you can also look at the itinerary for Germany/Austria/Switzerland and modify it by starting in Amsterdam. You could substitute Cologne and the Rhine for Trier or Baden-Baden, etc.
In Germany, Berlin is a great destination (not on the above tour link) and served by relatively fast trains or by budget flights from Amsterdam (www.skyscaner.com), or could be a starting point, of course. In Austria, Vienna similarly has tons to see. Or maybe Austria's not key right now and you only meant to include a bit between Munich and Switzerland (in which case you would probably fly home from Zurich). In two weeks, Amsterdam, Berlin, Swiss Alps, and Vienna (for instance) would be stretching the distance you travel and 3-4 nights in each would not leave time for anything in between. So from that list, what might be a priority this time and what do you save for another trip?
A few suggestions ...
Amsterdam (3) >> Berlin (4) >> Dresden (1) >> Prague (3) >> Vienna/Munich (3)
Amsterdam (3) >> Rhine (3) >> Swiss Alps (3) >> Luzern (2) >> Munich (3)
Prague (3) >> Budapest (3) >> Vienna (3) >> Salzburg (2) >> Munich (3)
Vienna/Munich (3) >> Salzburg (2) >> Austrian Tirol (3) >> Swiss Alps (3) >> Luzern (2) >> Zurich (1)