Paper problems - Many of us, forget to keep adequate photocopies of important documents such as passport, or hotel booking confirmations while travelling. Some of these documents are important to validate your bookings or claims, lest your bags or originals get misplaced.
Burying it deep - We either are completely reckless about our documents or are extra cautious. I find that people dump their passports, etc, right at the bottom of the hand baggage fearing that it will get stolen. And then they have to dig through all that mess to pull it out at the immigration desk - now, how many times have you yourself witnessed this?!
Not confirming - Many rely heavily on agents or subordinates and assume that details like transport, etc, will be taken care of. Hence do not carry telephone numbers of the contact in that city, or detailed directions to the meeting place or hotel , not checking transport schedules or confirming meeting details before leaving can cause trouble
Flight trouble - Many arrive late for check-ins and end up with middle seats which are uncomfortable. Sometimes they even miss the flight
Forgetting essentials - Forgetting to carry enough business cards, and laptops and cell phone chargers or plug pin adaptors is a very common mistake people
Cheap thrills - People generally tend to go in for the cheapest hotel deals, airfare, packages... everything. Cheap deals usually offer substandard service, one can actually land up spending more in irritation and distance and time
Not tagging your luggage - These days luggage and other travel accessories have the same designs the world over, this can be very confusing. "On one of my trips I took off with someone else's bag that had the same initials, look and feel as mine. I realised this only after reaching the hotel, due to which I was late for a very important dinner meeting. Since then my luggage always has a ribbon on the handle and my business card in the tag
Carrying too much - Many people carry more baggage than they are able to handle. This does not allow you to roam around freely in immigration and security. Also they fail to confirm with the airlines about baggage restriction - Many people want to carry laptops, handbag and their blazers all at the same time... relax and keep your cabin luggage light
Roaming reckless - Many people forget to carry their credit cards. Even if they do, they carry only one, which may not work due to some reason. Some international credit cards require that you call up the bank and activate the roaming feature, failing to do which your card will not work in another country, people also forget to check if the card is valid and has enough credit left before setting out.
Homework not done - Inadequate research about office timings, holidays and weather conditions in your destination will leave you high and dry. Also not knowing about how much you will need to spend, and if your bank has branches and ATM networks in the place you are heading to, will leave you without money in a strange country or area. Travelling is a skill you need to perfect, especially if your job requires it. The more you travel, the better you'll get at it. Till then, PLAN your work trips better.