We usually are not aware of the varying levels of language we use when speaking to different persons in our lives. However, we do speak differently depending upon where we are and to whom we are speaking. When we engage in personal conversations with our peers, we choose different words and phrases than we do when speaking to our children. While it is appropriate to use slang or make grammatical errors in our informal interactions, when we are in formal settings, such as a job interview or the workplace, speaking professional English puts us at an advantage.
Keep a digital voice recorder with you and record yourself in natural conversations with friends. Play the conversations back and jot down in a notebook any informal speech patterns you notice. Include slang terms as well as incorrect word usage. For example, saying, "Then I go," when referring to something verbally expressed rather than the correct form,"Then I said," is incorrect.
Keep recording your conversations over a period of several days and continue to note the informal patterns, especially the ones used repeatedly. Get a friend to join you in listening to the recorded conversations and to assist in identifying the informal speech pattens.
Write down alternate words and phrases to change the recorded informal expressions into more formal expressions. Examine nouns and verbs for singular/plural agreement. For example: "They was laughing," becomes, "They were laughing." Change incorrect use of adjectives into adverbs when necessary. For example, "He walked slowly," is correct. "He walked slow," is not correct.
Use an English grammar book to correct your usage of words, phrases and verb tense. A good grammar book will provide examples of correct sentence structure. These texts are available in most bookstores. There are many online resources as well.
Practice formal speech with a friend. Begin your conversation as you normally would, then switch to a more formal mode of expression. Have fun correcting each other. Exaggerate the formality to highlight the differences between formal and informal speech. For example, instead of saying, " My sister put the food on the stove," try saying, "My sibling placed the culinary delights on the apparatus designed for chemically enhancing the victuals." Use a thesaurus to find alternate words for those you repeat frequently.
Choose a topic and engage in a formal conversation with a friend. Pretend that the conversation is taking place at work. Record the conversation. Play back the conversation and make note of any informal usage. Practice frequently.
Be vigilant when you are in the workplace and constantly keep in mind the difference in speech patterns that you have learned.