While I usually use flight (and hotel) search engines, I also double-check the airline or hotel own website for prices and promotions.

My go-to search engines, when it comes to flights, are usually CheapOair.com, Trip.com, kiwi.com, jetradar.com, and Google flights.

After I have my flight, accommodation is the next thing I book. If it is an urban trip, I would usually start with hotels.com (where you get 1 night free after booking 10), agoda.com, hotellook.com or booking.com. If you are traveling Asia, than 12go.asia is what you need!

If you are looking for a more luxurious stay, I recommend Hilton where you can collect points (it's free to join) for endless possibilities.
Finally, Sanatory is an online service dedicated to booking recreational vacations and retreats in sanatoriums, pensiones and spa hotels.

Another way to travel is to swap homes. Vrbo is part of Expedia Group and offers homeowners and travelers a platform to do so.

When it comes to car rentals many go straight to the big names, but I find them very expensive compare to other options. EconomyCarBookings.com is usually the cheapest, but sometimes there are better deals, I always do my research using these sites as well: RentalCars.com, MyRentacar.com, autoeurope.com and discovercars.com.

When traveling without a car, you will need transportation. In my experience, omio.com, Trainline and RailEurope are some of the cheapest place for trains, buses, and flights.

No matter where you go or what type of trip it is, ALWAYS have a good travel insurance, I use VisitorsCoverage.com.

The last site I always use is matrix.itasoftware.com, it is a search engine where you cannot purchase a flight ticket, but you can find the best prices and it will provide you with all the information an agent would need to book that amazing deal for you.