When to book lodgings
How far in advance should I reserve my hotel rooms?
With three exceptions details below), there's no real need to book lodgings too far in advance.
Last-minute rates on unsold rooms at larger hotels aside, hotel rates will not vary too much depending on when you book—certainly not so much that it should be a deciding factor.
The key, then, is how much you have your heart set on a particular hotel. There will almost always be some room available somewhere. It's finding that perfect room at an amazing rate that takes a bit more planning.
Other than the three cases outlined below, I like to play it pretty loose with reservations and simply book ahead one day in advance—or even wait until afternoon to book for the evening. That way, I can let serendipity dictate my trip rather than too rigid a schedule.
First and last nights: Book two weeks out
I luek to reserve a room for the first and the final night of any trip.
This helps alleviate the stress of those travel days—the jet lag and chaos of getting into town, and again at the end with the nervousness of getting ready for the return flight (which somehow usually involves getting up insanely early, once you pad enough time for trasnport, traffic, and getting to the airport two hours ahead of time).
This technique also comes in handy if you have plane delays upon arrival, as you are at least sure there is a room waiting for you.
I once arrived in Bangkok nine hours late (thanks, NorthWest) but since I had already booked a room and paid for it—and prudently called ahead during my iterminable layover in Tokyo to let them know I would be arriving late—I was able to check in at dawn, yawning hugely, and sleep until noon.
Special hotels: Book ASAP
If it's a small hotel, or a special one, or some great family B&B or agriturismo or apartment in Paris or a particular beach resort and you are truly keen to stay there, go ahead and book as soon as your travel dates are firm.
Most hotels (and the better booking engines) have no-fault cancellation policies, usually up to 48 hours before arrival, so you have some wiggle room to change your plans.
Festivals and trade shows: Book ASAP
The other exception is when there are not enough rooms to meet demand, so check if there is a festival, major holiday, or big trade fair in town that coincides with your visit because that mean the rooms will be gobbled up pretty quickly and you will want to book as far in advance as possible.