Summer is travel season and a time for people to follow through on their plans to visit popular destinations. In the course of making travel arrangements and going through an itinerary, travelers may find themselves getting hit with some unexpected charges. Mental Floss and Discover have created a list of some of the most common hidden fees that can put a dent in your vacation budget—and how to avoid them.

1. Telephone Flight Reservation Fees

If you have questions about booking a flight that aren’t easily answered online, it can be tempting to phone an airline to get clarification. Unfortunately, you might spend time on hold and in dialogue with a representative before you realize there’s a surcharge for booking the ticket over the phone. It’s better to call an agent for information but complete your transaction on the airline’s web site.

2. Frequent Flyer Fees

When you fly using an airline program and accumulate miles, you’re supposed to be able to redeem them for free or reduced-price tickets. Be mindful that some airlines will hit you with late-booking fees if you purchase a ticket for a flight that leaves in a few days or weeks. Be sure to plan far enough ahead if you want to cash in your miles without a penalty.

3. Rental Car Fuel

If you’re strapped for time, you might be tempted to return a rental car with less than the full tank requested by the rental agency. Unfortunately, they won’t just charge you for the price of the gas. You might be hit with a surcharge of up to a few dollars per gallon. To prevent any surprise charges on your credit card, make sure you hit the gas station before turning the car in.

4. Rental Car Toll Fees

Think your rental car takes care of tolls with a windshield transponder? It might, but not without a price. Some rental agencies charge $10 or $15 for passing a toll booth using their car-mounted pass. Try to avoid toll routes when possible or have change ready so you can pay them yourself.

5. Airplane Pillows and Blankets

Want to catch some rest on a long flight? Be prepared to pay at least a few dollars for an airline-issued pillow or blanket. It’s better to bring a travel pillow and a light throw with your carry-on luggage instead.

6. Cruise Fees

A lot of cruise lines promise tickets that are all-inclusive, but that definition can vary widely. Before booking, make sure things like food and entertainment are covered. If not, see if your budget can accommodate all of the fine print attached to the ticket.

7. Hotel Resort Fees

Find a great nightly rate on a hotel room? Be aware that some chains will give you an advertised price, but the “final” price will have extra charges. Hotels call these charges resort fees or destination fees and say that they cover amenities like Wi-Fi, towels, and gym access. You probably can’t avoid them, but make sure you factor them in when deciding where to book your stay.

Keeping track of your travel finances is a smart move. Another smart move? The Discover it® Miles Card will earn you 1.5X miles for every dollar spent on purchases and those rewards never expire. Plus, at the end of your first year, Discover will match all the miles you’ve earned automatically, which you can put towards another awesome vacation. Visit Discover.com/Travel to learn more!