Hotels tend to book up in high season like during European summer, and during Winter and Spring Break. Luckily, this isn’t the time when most people will be taking business trips, because business tends to slow down during these periods. In any case, to avoid finding a hotel fully booked, be sure to book as far in advance as possible, and your business travel plans permit. You may get cheaper rates if you book two weeks in advance, as prices tend to fluctuate depending on the time you book.