What to visit in the Netherlands ?

Always the same while on vacation abroad : so many things you want to see and do, and so little time.
Two basic options : rushing around with a very loaded program or going for the slower in-depth approach.
If you looked around on this site, it will be clear that it advocates the slower in-depth approach. Being picky and taking your time. And do consider the immense advantages of flexibility, especially for this country.
But the choice is yours, of course.

So, make a list of places you absolutely want to see with your own eyes. And if you plan to spend a couple of days in or around Amsterdam, consider a day trip to this region with its fortified towns in an historical countryside.
Train station Weesp for a visit to Weesp and Muiden with its castle (the distance Weesp - Muiden is about 2 km ; Weesp - Naarden about 8 km).
Train station Naarden-Bussum for fortified Naarden (about half an hour walking from the station).
Or for a wider range, rent a bike at either station. For a round trip Weesp - Muiden - Naarden - Weesp, count about 30 km (depending on your route) and ½ day for speedy sightseeing. Reckon on a full day with visits to castle and Fortress Museum (or other), and a stroll in the fortified towns.
If you want more in depth historical background information, you can decide on a guided bicycle day trip as described in this site. See the What-pages.

In all cases, if you want to get the most of your trip to Holland, some advice "from the field" might come in handy.
Because there is so much more than these "official highlights", where tourists are shipped by the packed busload.
If you're interested in history and culture, and leave some air in your schedule, we can talk. And we can start talking right now, by email. That's absolutely for free !
If more extensive research for your plans is needed, the meter only starts ticking after mutual agreement.
Also during a guided day trip as a start of your vacation with a general introduction to the history and culture of the Netherlands, there's plenty of time to discuss your further discovery of Holland (of the whole country, not just the region of the day trip, of course).
A separate introductory chat and brainstorm-session at your arrival is another possibility. See lecture.