Even the most meticulously planned trip is subject to snafus, but with a little insider know-how, you can avoid making the common mistakes that can derail a vacation. Stick to the guidelines below, and you're more likely to have a trip that's memorable not for lost luggage and rushed sightseeing, but for the thrill of discovering a new place and savoring it.

Not booking enough connection time between flights

Leaving a window of at least an hour and a half between connecting flights will significantly drop your chances of missing your flight or having your luggage lost, says Sally Watkins, travel agent at Century Travel and Cruises in Austin, Texas. Having only 45 minutes to connect between flights might seem doable-not to mention the siren call of less lag time spent hanging out at a dismal food court-but it's often not enough, especially in large airports where the gates could be far apart. Don't rely on airlines to do the math for you, either: "Flights can't be booked unless it is a legitimate change time according to that airport, and usually if it's the minimum change time and airlines let you book that, they will make it work," Watkins says.

Not applying for your passport early enough

Routine passport processing takes about four to six weeks, so as soon as you start planning for your trip, apply for a passport if you need one, or make sure the one you already have hasn't expired. Plus, in certain countries you need at least six months' worth of validity remaining to enter, says Elizabeth Finan, spokesperson for the State Department's Bureau of Consular Affairs. (Go to travel.state.gov for more information.) If your trip is coming up quicker than that, you can shell out $60 to cut the processing time to two to three weeks, but if you're planning to board a plane in less than two weeks, make an appointment at your local passport agency by calling 877/487-2778. The $60 fee still applies. If you've traveled so much you've practically worn out your passport, flip through it as a precaution: "Frequent travelers should make sure that they have enough pages in their passports," says Finan. "For example, South African law requires travelers to have one fully blank visa page in the passport; without the requisite number of pages, you may be refused entry." No one wants that.

Underestimating the location of your hotel from the city center

When you're visiting a city, ponying up for a more expensive hotel that's in the middle of the action can be a better financial decision in the long run than staying out in the suburbs and spending money and time on transportation. Use time you save to explore-or just recharge in your hotel room. "Particularly if it's a European city in the month of July and it's hot... you're going to want to go back in the late afternoon and put your feet up before you go to dinner," Watkins says. "That's not easy to do if your hotel is a 30-minute bus ride away." Plus, if it's a family vacation, toting kids on unfamiliar trains or taxis with few breaks will increase the possibility that you'll have a frustrating visit. "Value is more important than what's the cheapest," Watkins says.

Trying to do too much in one trip

Allot a minimum of three days for visiting major cities like Rome, London, and Paris, and you'll end up with a richer vacation that includes time for simple pleasures like people-watching or relaxing in sidewalk cafés, says Watkins. "A lot of people say, 'I just want to do just one night in whatever and one night in so-and-so.' Slow down! By the time you either load all the bags into the car, drive, and park, or you schlep all the bags onto a train, you don't have that much of a day left," says Watkins. The same goes for multiple activities. Make time for wandering around. In Rome, for example, planning to see the Vatican Museums, the Colosseum, and the Forum in the same day is overkill, Watkins says. Really seeing the city via strolls and serendipity can be invaluable.

Not being honest about your interests, likes, and dislikes

There's no shame in wanting to leisurely sit in cafés in Paris instead of hoofing it to every monument-or preferring to check out Mayan ruins in Tulum instead of lying in a hammock. Before you plan vacation activities that others insist you'll enjoy, sit down and think hard about what you want your trip to be, then follow your own itinerary. "Many people plan the trip they think they ought to want, rather than the trip they actually want," says Edward Hasbrouck, author of The Practical Nomad: How to Travel Around the World. "If you rarely set foot in a museum, why plan a trip with museum after museum? A lack of self-awareness can lead to, among other things, relying on recommendations from people with very different tastes." Your trip, your experience.

Read more from Budget Travel (Page 2) >>