Writing a letter to a friend about to embark on a trip is a nice way of relaying important travel and safety advice, as well as giving tips on places to go, if you have been to that destination yourself. Mention how much you value your friendship. This does not need to be done in a somber way. Let your humorous side shine so your letter will be informative and entertaining.
Write some colorful details about the place your friend is visiting. Make the advice engaging by talking about a funny incident that took place while you were there, if you were there. If you have not visited where your friend will be, give helpful advice. This might include: to check with the concierge for interesting places to visit and be sure to double-check your room before leaving.
Discuss a mutual trip you and your friend went on. Talk about the funny parts as well as the sadder parts. Draw a picture in words about the places that you saw and the fun you had.
Mention any warnings related to your friend's destination. If he is going to a place for which a travel warning has been issued (or special precautions such as to use bottled water only), this might not be the best time for making jokes. There could be dangers your friend may encounter. If this trip is part of a volunteer job-related trip, congratulate your friend on being dedicated to helping others. Tell her you hope for her safe return.
Be informal in your writing. The first paragraph is a summary about why you are writing; the body is composed of the main ideas; the last paragraph expresses a general wish for good, safe travel. Write the letter in your own hand to give it an added personal touch.