Devote some regular time to building your vocabulary. This can be daily or weekly, half an hour or much longer. Setting aside time to work on this task increases your chances of retaining what you learn. You will surely acquire new words and expressions in casual conversation, but remembering their meaning can be strongly enhanced by seeing them in print, saying them aloud to check pronunciation, looking up meanings in a dictionary, or other memory-enhancing tasks you need time and quiet to do. Keeping a list of words you have studied in this planned way will encourage you to persist.
Focus your progress by deciding what kind of vocabulary you need to build. Perhaps you need more technical vocabulary for your job (which is often the case when technology shifts). Supplement user manuals and training sheets from work with a trip to the technology section of the public library; learning more about wind turbines in general, for example, may make it easier to grasp directions for the specific machinery you work with in that field.
Search out magazines in areas that interest you. Magazine language aims at a wide range of reading abilities, and pictures are designed to enhance meaning. The special-interest focus of most magazines---sports, fashion, health---also means that they are likely to use a fairly repetitive vocabulary, which allows you practice words frequently.
Explore online vocabulary-building websites and services. Many of them are free and offer games and puzzles as well as more formal practice. Sites may have special sections to help clarify idioms and slang expressions.
Watch television and go to the movies. Pronouncing words correctly is easy to learn when you can watch the face of another person saying the word. For example, a child who sings "Row, Row, Row Your Bow (Boat)" or "Baa, Baa, Back Shee (Black Sheep)" may well have learned the songs by hearing a tape rather than watching and listening to another person sing.
Read a daily newspaper, either in print or online. Like magazines, newspapers are written specifically to tell you things. They let you see the names of people and places you hear on the TV or radio news in print. Some articles will explain events more fully than broadcast news, including political, military or other terms that may be new or puzzling to you.
Have fun with words by playing games. Scrabble, Boggle, crossword-puzzles and word-searches all challenge your vocabulary in amusing ways. You are likely to emerge from almost every word game with a new word in your vocabulary.