For travel booking I use metasearch websites to find accomodation and flights. Metasearch sites search booking sites for the best deals and allow easy and quick comparison.
Flights
Matrix Airfare Search is an excellent website for finding cheap airfares.
Hotels only
hotels combined - gives a useful location map with hotels noted. Good for complex searching with many filters.
Hotel cancellation
Hotel bookings are often easily cancelled, without penalties. So if your plans change, or you find a better deal, cancel the booking.
Hotels or flights
Booking sites from that country are also worth checking because they list extra options. e.g.:
Thailand: Sawadee.com
Suggested process to find the best price for accomodation or a flight:
Search on at least two metasearch sites.
Search on at least one booking site from that country.
Check the price directly from the hotel or airline website.