With nearly 8 million travel sites out there to choose from, how can you know which travel sites are best for trip planning.  And how do you know where to start?

Once you know where you want to go, you’ll need to figure out how much it’s going to cost.  These days there are plenty of great travel sites to aid you in that process.

One of the best for U.S. travel is Kayak.com, which compares fares from virtually all American airlines.  When you find a fare you like, just click on it and you’ll go to the airlines website for booking.  One of the best features is the flexible-date option, which shows you which days of travel are least expensive.

Sometimes, just shifting your dates a couples of days can save you hundreds of dollars.

Sidestep.com is another reliable travel site for domestic airfares.  It searches more than 600 sites for information.

You may have heard about European discount airlines like EasyJet and RyanAir that offer really cheap airfare from London to Paris or Rome.  Fares can be as low as $2 one way.  But virtually every service is an additional charge.

If you’re not carrying any luggage and you’re willing to forego anything that resembles service, these can be a good deal. 

You can find these fares on Dohop.com.  Just make sure you read all the terms and conditions carefully because there are many unsatisfied customers.

Lately, the airlines are charging for whatever they can, and some are now charging for advance seat assignments.  On long-haul flights, this can add hundreds of dollars to the price of your ticket.  So before you pay extra for an aisle of exit-row seat, you should make sure it’s worth the additional charge.

Travel sites like Seatexpert.com and Seatguru.com can show you where the best seats on every flight are. 

With your flight nailed down, the next step in travel planning is researching places to stay.

More than 25 million travelers have published their candid hotel reviews on Tripadvisors.com.  For this reason, lots of vacationers start their research there.  It has a wealth of information, that’s for sure.  But be sure to check sites like Fodors.com or Frommers.com for professional advice. 

If you’re planning a trip to Europe, Venere.com includes lots of smaller hotels and inns that the bigger travel sites don’t represent.

If you’re planning a trip to Europe, Venere.com includes lots of smaller hotels and inns that the bigger travel sites don’t represent.

Oyster.com is a new site that sends incognito journalists to hotels to photograph and write up their experiences.  Their reviews are pretty in-depth.  But they don’t cover many destinations yet. 

Nowadays, most of the hotel sites are owned by a couple of parent companies, so there’s not much point in comparison shopping online.  A search of seven sites will likely yield the same price on most of the sites.  If there is a substantial difference, be sure the room type if the same. 

A good deal on a hotel’s least expensive room probably won’t turn out to be a good deal after all.  Chances are high that you won’t be happy in any hotel’s cheapest room. 

We don’t like to prepay for hotel rooms.  And many of the bigger sites are now requiring it for their best deals.   If the prepaid, nonrefundable rate is a tremendous savings, see if the hotel will honor it without paying in advance.  Otherwise, be careful.  Getting stuck for 100% is a lot to sacrifice for saving 15%.

And if you’re traveling off season or going to an area with low occupancy, consider going without making reservations in advance.  You might be able to get the best deal yet by negotiating on the spot.