Reservations Needed for Amsterdam - Leiden Train?

No need for reservations for a local train ride between Amsterdam and Leiden . It's practically a commuter train.

Reservations aren't even possible as on no train in the Netherlands.
You'll get sooner in Leiden when you change in Rotterdam, where the Thalys also has a stop. Train for Leiden leaves every 15 mins, alternatingly with »Amsterdam Centraal« or »Lelystad Centrum« as final destination. Check the trainplanner of the Dutch railways.

First, since Thalys trains all stop at Schiphol, why go all the way in to Amsterdam to then go abck? You can catch the train to Leiden at Schiphol.

But even better, why not take the same Thalys train you are looking at and leave it in Rotterdam, wait 10 minutes (appx), and have a train to Leiden from Rotterdam, in 1/2 an hour you will be in Leiden Centraal, at the same time you would have been arriving at Amsterdam Centraal.

(Tom types quicker, he posted above while I was writing)

We loved using Leiden as a base to explore The Netherlands. The train transportation is excellent. We stopped looking at schedules as there always a train heading towards Rotterdam or Amsterdam in a short time. Buy an OV Clipkaart for buses, trams, used all the country. We bought ours at Keiden train station. Fill it as needed. When you arrive at any stop by train, you can then use the card to jump on a tram or bus. Enjoy beautiful Leiden.

Leiden is a great place to visit, as are many of the small towns surrounding Amsterdam.

But why are you going back to Leiden from Paris? By the time you check out of the hotel, get to the train station, and then ride to your destination it's going to take about half a day. The best of Europe tour starts from Amsterdam so you were already there. An open jaw ticket is not that much more expensive than round-trip. If it's not too late you should look into going to Leiden before you start the tour and then flying back home out of Paris.

Buy an OV Chipkaart
In general that's a good advise, but if you only plan a few day trips it's better to buy separate tickets. The OV Chipkaart costs EUR 7,50 and needs being loaded with at least EUR 20 to be able to use it on the train. You can get the unused money refunded at the end of your trip, but it will undoubtedly come with some paperwork at a ticket window.

And a practical point: Leiden Centraal is a so-called »closed station«, meaning it has metro-style gates which have to be opened with your ticket. The barcode or QR code on your Thalys ticket should do the trick. If you have any problem, there is an information pillar near the gates to summon personnel to open it for you.

Wow! Thanks for all the tips. It never occurred to me to get off at Rotterdam. Or Schipol. I'll check out the trainplanner.

John, my DH wants to spend more time in the Netherlands. We are arriving a few days before the tour, and staying in Haarlem. But we had about 4 or 5 days after the tour available, and he wants to go back. We chose Leiden because it looks interesting, has plenty of train connections to other cities, and we've never been there.

Thanks again, everyone.