Set goals. Decide the top three tasks you want to learn over the telephone. Try a variety of challenges to enhance your work and your home life by learning to use business English and have social interactions on the telephone. For example, you may wish to learn to place a take-out order for egg rolls or pizza, call a taxi or telephone a friend who's been ill and ask if they're feeling better.
Determine your target language, which may be more formal over the telephone than you would use in speaking face-to-face. Prepare exactly what you want to say. This will help you to not be nervous. Write out your key words, phrases, sentences and especially questions you wish to ask. Learn special telephone terminology such as "hold on" and "hang up."
Practice saying the words you will be learning to speak on the telephone. Say them aloud to yourself or to a friend. Record yourself and play it back if you have a recorder. Make use of computerized pronunciation devices, finding one as close as possible to the tasks you hope to accomplish. Listen and practice again.
Make the actual calls in which you will learn to function in English over the telephone. Start with one easy, direct call to ask directions or place an order for food. Then go on to a more complex, problem-solving call to a bank or other business. Finally, test your ability by having a conversation with a friend or colleague.