Take an English-French dictionary with you. You will need this book for reference regularly, so you will want to buy one that packs easily and is easily accessible. Electronic versions also work great as long as they are handy and the device stays charged.
Seek out situations or activities that require you to hear and see French language. You will need to make a mental effort to take in what you see and attach meaning to it. Rather than just hearing and seeing, you will want to listen and read. Use your resources, such as a dictionary or electronic resource, to decipher unfamiliar language.
Watch local TV programming when you have the chance. For example, in your hotel room at the end of the day when you are not doing anything else. French TV often has English channels with French subtitles or French language programming. Depending on your language level, either of these options will be helpful opportunities to finish your day with learning.
Pick up pamphlets at museums and sites you visit. These materials tend to be written in several languages and allow you the opportunity to compare your native language with French. You can go back and forth, reading each version, until you can tie the two together. Pamphlets also make free souvenirs to take home.
Talk to people you meet. Chances are most people will be interested in meeting someone from another country, just as you are interested in meeting them. Try talking in French. You can start with just a few words and build from there. This gives you a chance to practice your skills while you continue to improve your language knowledge. You may even pick up some cultural knowledge and make new friends.
Set goals for yourself. If you are serious about mixing business with pleasure, or in this case learning while traveling, you will need to set some goals and balance your time and effort. Setting goals for yourself is one way to make sure you are progressing in your language skills. Set your goals according to the time you want to invest and be realistic, as you do not want to stress yourself while on vacation. A goal can be as simple as learning and incorporating 10 new words a day. Chances are you will learn more than you realize at the end of the trip.
Play games or entertain yourself in French. Traveling often involves a lot of down time. Whether you are on an airplane or a train, you will need some mode of entertainment. This is an excellent time to increase your French language knowledge. Take flash cards or a language-learning book to expand your vocabulary. If you are advanced, you can read a French language novel or write in your journal, in French, about your travels.