In order to travel as much as possible I try to ensure that I'm saving money by using good travel resources. This page lists the several of the websites that I commonly use when planning out a trip.
One of the best comparison sites for finding flights is the well-known Expedia, which consolidates all of the various airlines into one convenient location that often finds better deals than their competitors.
Another popular and consistently good option is Priceline. They offer extremely competitive prices and make it easy to check several sites at once or put notifications on to update any price changes to tickets.
A less known site is Jet Radar which is also a comparison flight finder that sometimes finds cheaper flights for smaller airlines. I generally check these two search engines against the actual airline apps (primarily Delta and United) to see if it is more cost effective to buy a ticket or use frequent flyer miles.
This website offers savings on hotels all over the world in over 120,000 different destinations. It allows you to browse hotels and offers the best options for all budgets. It can sort by destinations, a map in the city, or the property rental type from private villas to youth hostels. Properties are also ranked per city and include reviews from guests.
This is another website that allows you to compare the prices found from various agencies on popular hotels all over the world. It displays the price, ranking, distance to city center and type of accommodation and also offers a variety of options for every budget.
Generally I try to explore cities as much as I can by myself. It saves money and enables me to only visit the places I really want to go. Yet, sometimes using an organized tour is actually much cheaper and easier. On extended trips like hiking the Inca Trail to Machu Picchu and doing the camel trek into the Sahara in Morocco, using a tour was a million times easier than coordinating the required logistics and probably saved a good deal of money. I have also used Viator to book many day trips as well including a visit to Monet's Gardens, a tour to visit Windsor, Cambridge and Stonehenge in a day, and a wine tour in Santiago. They have multiple options for tours offered and at very reasonable prices!
If I am not finding a specific tour that I want on Viator, I check out what is offered on Trip Advisor. They tend to have very similar (and sometimes the exact same tours), but they occasionally come up with some alternate options. They also are an excellent starting point for organizing the type of search according to the activity or location.
One of the best options for learning about the history of a city and seeing the most notable locations and buildings is taking a free Sandeman walking tour. Offered in many cities primarily around Europe, tour guides take groups on a tour of the city for usually 1.5-3 hours explaining the most interesting parts and historical tidbits. They are free tours and only ask participants to tip whatever the value they feel they experiences, which ensures anyone can join and takes off pressure for an expected tip. I have done these tours so far in Prague, Amsterdam, and Brussels and each time have been pleased to find that the guides were very informative, engaging, and I learned quite a lot about the cities.
Disclosure: Several of the above websites contain affiliate links. If you click them, I may get a small percentage of your purchase which adds no additional cost to you, but helps with the overhead for keeping this site up!