Need to book early?

You'll need advance hotel reservations in Amsterdam and Paris. There is no off-season in Amsterdam anymore, hotels are full year-round. Also, I believe the first week in March is when the fashion shows occur in Paris; these fashion shows tend to fill up the hotels.

Joe,

Absolutely book early for Paris. There are many influences outside of normal tourists that go on in Paris - sporting tournaments - large conferences - etc just like any other large city. Assuming that it is "off season" typically means your prices are lower - but getting your preferred hotel can be a problem if you wait too long.

I am booking all hostels ahead of time.

If you don't especially care where you stay, you don't need to book in advance. But if your trip will be the worse off if you can't stay in a particular hotel or neighborhood, it's worth nailing that stuff down.

In any case, if you know you are arriving March 5th, why not reserve now? It's be one less thing to worry about and one more certainty to base your trip on.

Even people who like to wing it often book ahead for their first night or two, to avoid the stress of getting off the plane, be jet-lagged and not knowing where you're going to sleep that first night.

If you already know your dates just go ahead and book. That way you have time to choose the best best hotel for you. We're going in June and we've had our hotels booked for 2 months now.

Tim, I'd be sure and reconfirm those reservations before you go. On one memorable trip, we booked accomodations in November for an April trip. Over the turn of the year, when finishing out their books for the year, two of our B&Bs lost our reservations. We had printed copies of the original confirmations with us, but that didn't do us any good when the rooms were full.

I always travel shoulder season and have never gone homeless.

I like to book for the first night of my trip so I have one less thing to worry about that day.

After that I just call ahead in the morning and have no problem.

I once arrived in Munich on the first day of Octoberfest with no reservation (and I didn't call ahead that morning). I made more calls that day than any other (and began to worry). Even then I ended up at a very nice pension at the normal rate.

I had missed a Castle Hostel on the Rhine because it was full, so next trip I did get reservations. If there is a place you really don't want to miss that is normally busy, booking ahead may be a good idea. Other than that you really don't need to book ahead.