booking.com only. Never had a problem and use it about 15 times/year
I use booking.com too, though you can get caught if going to somewhere where there is a big event and then every hotel might be booked out, leaving just the €300/night ones, and you don’t ask them about their cancellation policy 
Happened to me in Brussels once.
Air B&B has also produced some spectacular results and Justine and I will try to book an apartment for the Prague fly-in because by the time you get to 3 or 4, self catering is usually much better value.
I try to avoid sleeping in really crappy places if I am going to fly the following day 
Most hotels below the €100 level have crappy beds, no aircon, often stink of smoke… If I am staying in some real dumps in the summer (often the case in Greece) I carry a mosquito net!
I keep it simple and always use Accor group hotels where possible and book way in advance.
They all (whichever brand) have a very good cancellation policy (1800 on the day of arrival).
But they’re not in every town…
My tactic last year was to have a responsible person back at base (usually the Mrs) standing by for a text from me to say I have taken off and we were en-route. She would then book a room/rooms with Booking.com to our agreed specification. When I arrived at the next stop, I would get a text from base giving the address etc to be shown to the non-english speaking taxi driver. No worries about cancellations. Worked perfectly every time.
Only time i did this i stopped on a strip with walkable distance to the hotel (Troyes in FR) and booked in advance a cancellable room with booking.com.
(I also had cancellable train tickets in case of bad weather as this was a “must go” event)
My tactic last year was to have a responsible person back at base (usually the Mrs) standing by for a text from me to say I have taken off and we were en-route. She would then book a room/rooms with Booking.com to our agreed specification. When I arrived at the next stop, I would get a text from base giving the address etc to be shown to the non-english speaking taxi driver. No worries about cancellations. Worked perfectly every time.
I wish I had an ops department like that…
Whenever traveling with my wife I ask her to choose since her standards are a lot higher than mine :-). That’s how we ended up in a different hotel than the rest of the EuroGA participants at the Calvi fly-in last year.
Booking.com are really good because of the cancellation policies, and because they offer a list of conveniently located hotels that match your criterias, reviews and reservation on the same site. Chasing down a hotel the old fashioned way using yellow pages is time consuming.
But a lot of hotels, especially the smaller ones, hate them because they take a significant fee.
If you’re flexible (i.e. flying somewhere “for fun”) you can find great deals when booking on the day of departure.
Hotels tend to withhold a certain amount of rooms, not visible on the internet, but they will be put online last minute when they’re not booked through traditional channels.
Or rooms that become available after a cancellation. I regularly find decent rooms with 20% – 40% reduction.
When I need to be somewhere at a certain place and time, I book well in advance and check the cancellation policy.
Booking.com usually offers the same room for two prices: The more expensive one can be cancelled without additional cost; the cheaper “special conditions apply” comes with a cancellation fee.
What you should try to avoid at all costs is to ask a taxi driver to drive you around, looking for a hotel.
I did that once after a diverted night landing at Munster Osnabruck. There was no airport hotel and the first 3 hotels we tried were all closed. The taxi bill was around 40EUR.
So, also take hotel availability into account while planning your ALT’s ;-)
But a lot of hotels, especially the smaller ones, hate them because they take a significant fee.
When I book it myself (usually our OPS department looks after our accomodation) I will look up a price at booking.com or HRS.com and then call the hotel directly, telling them I know their online price. One usually then gets the same price (or even better) and they don’t need to pay their online booking fees.
Where we have a handling agent we often book hotel accomodation and transportation through them because they tend to get unbeatable rates (like 15 Euros for crew transport where a taxi would be 50 or more). And cancellation is no problem either.
I also book hotels like this, i check first Tripadvisor for reports and booking.com for prices, but i finally book at the hotel itself…. the fees they have to pay this booking plattforms are are quite high.
