Seven ways to run over budget (and how to avoid them)

You've taken care of the big-ticket items for your vacation, but you're still worried about "little" things fraying your budget.

What are you likely to overlook?

1. Food

In my home region, food is ridiculously affordable: junk food even mores. That's not true in other places, which is probably a good thing.

When you travel, even if you stay in a hostel and have breakfast there, much of the food tends to be high in carbs. This makes you hungry sooner than if you started your day with a protein-rich meal.

If you planned to have a hostel breakfast and one more "regular" meal -- a good way to save money -- that bigger meal might come earlier than suppertime, because you're hungry from all those fast-dissolving carbs. Then you let yourself have a snack around, say, 6 p.m. local time, because the fullness from your second meal wore off. To wrap up the day, you have one last snack before you go to bed, because who wants to go to bed hungry?

Now you've spent the cost of a third meal and maybe a little more. If you had a snug food budget, you just blew it for the day.

How to avoid it - stick to your budget; buy meals instead of snacks; and keep some dense, high-protein food on hand, like peanuts or sunflower seeds. If you're having breakfast at a hostel, look for foods like yogurt, meat (if it's offered and if you eat meat), or peanut butter on toast. Shop at grocery stores instead of convenience stores.

See also - Eat on the cheap

2. Drinks

At home, water may be complimentary in restaurants, and refills of your pop (soda), coffee and tea are often also included.

Many, even most, other countries run things differently. Expect to pay for every glass or cup of liquid that you order in a restaurant, including water.

You don't realize how much you drink in a day until it costs you money. But you don't want to get dehydrated, either. With drinking fountains unusual to non-existent in many locations, it's hard even to travel with a water bottle and refill throughout the day.

How to avoid it - include drinks in your budget, and when possible, choose hydrating drinks like water. Alcoholic drinks dehydrate you more than they hydrate you. If the water is drinkable in your overnight lodging, fill your water bottle there. When you do go to a restaurant, drink everything you order.

3. Airport expenses

Oh, those airport money traps. You're a captive audience (who wants to go through Security a second time?), you have time on your hands, you're hungry, you're thirsty, and you know you won't get much food or drink during the flight.

That's how you end up spending $20 for a small drink, a couple bagels and a side order of some food you probably wouldn't even eat - let alone pay for - at home.

How to avoid it - airports are more likely to have drinking fountains than surrounding cities are, so fill up your water bottle there. You may be able to take snacks, or your snacks may be confiscated; every airport is different. Take good, protein-dense snacks in case you get away with it, and if you lose your food, buy better "snacks" than empty carbs that just make you hungry again.

4. Rental cars' extra charges

Aren't rental cars the most wonderful convenience?

Not always.

It starts with your time at the rental car counter. You thought you paid everything in advance, but now you owe extra money for fuel, insurance and who knows what else. The cost of your rental car just doubled.

After you get the car, where do you park it? The parking space may be farther away than the nearest bus or subway stop. It's anything but convenient.

How to avoid it - don't rent a car unless you can't get where you're going any other way. Don't pay for a rental car unless you know all the charges up front, including taxes, drop-off fees and automatic toll costs. Asking now - sometimes asking multiple times - saves you money later. Don't rely on third-party rentals or online reservations; pick up the phone and talk to a live person. You might even get a lower rate or an extra you weren't expecting, like free pick-up when you get the car or free drop-off at the train station.

5. Ground transportation

Parking costs, if you rent a car, easily add $20 a day to your budget in a bigger city. Depending on how far you drive and in which state or province, tolls can be just as expensive. We joked while driving through part of Illinois (near Chicago) that we paid a toll every mile.

Then there is the cost of public transit. Don't make the mistake I made in Boston, where the Silver Line bus was free from the airport to the station close to our hostel. I thought that was great, until I realized that I still had to pay bus fare to travel anywhere else, including back to the airport.

Costs from commuter rail, or Metros, add up.

How to avoid it - if you rented a car, choose accommodations that include parking (or know ahead of time what you will pay for parking). If you're relying on public transit, compare the cost of a daily pass, which most cities offer, and the individual trips you need to make. Remember that you'll probably "waste" a trip or two that takes you to the wrong place as you acclimate yourself to a new locale. Don't stress about that; just budget for it.

6. "Necessary" purchases

You didn't bring enough socks. You left a shirt on top of the dryer at home. Your deodorant and toothpaste are still on the kitchen counter in your one-quart bag.

What were you thinking?

How to avoid it - pack smart, double-check what you pack, and include an extra couple pairs of undergarments in your personal item or carry-on if you're flying.

7. "Unnecessary" purchases

Yes, souvenirs are cool. Yes, you want things that remind you of the wonderful trip you took.

But bulky souvenirs are often a waste of money and resources (especially if they're plastic, which already clogs our water ways). For a continuing insult, trinkets may throw your bag over the weight limit, costing you even more money.

How to avoid it - if you must buy souvenirs, make them lightweight, inexpensive and responsibly sourced. For example, we buy refrigerator magnets made where we travel; they don't cost much, they don't weigh much and they still give us happy reminders of our travels. A fast-becoming-favorite of mine is high-quality chocolate or baked goods. Even if additional duty fees are involved, it's consumable and appreciated: a "taste" of your adventures you'll savor later.