First up, contact the hotel direct. Nowadays most rates from booking sites can be matched or even beaten by going directly to the property itself. If booking online, try to ensure you always use your browser’s incognito mode to ensure your search history doesn’t affect the prices you see! Get in on the rewards program of the bigger sites (booking.com, trivago, expedia etc) and you’ll receive membership rewards and exclusive discounts.
Booking accommodation is no longer just about hotels and guesthouses. The sharing economy has brought heaps of options including home rentals (Airbnb and Homestay are good examples), Couchsurfing or even housesitting (try TrustedHousesitters or Nomador).