Search online for daily word building exercises. Places like The New York Times' website contain daily word builders to increase your vocabulary. Write them down and be challenged to use them in different forms, whether that's writing them in an email or using them in conversation.
Read a daily newspaper. USA Today is written on a basic, eighth-grade level, but newspapers such as The New York Times, The Wall Street Journal and The Washington Post contain more complicated words. A study published by Barbara Palmer in 1989 reports that students who read a daily newspaper increases vocabulary, reading comprehension and writing skills.
Learn word roots to expand quickly. Study the etymology of words to find out what the root means. The root word "scrib" means "to write" which transfers to other words like "manuscript," "scripture," "scribble" and "scribe." In this case, learning one root can easily add at least four words to the list. According to the book "Word Smart: Building an Educated Vocabulary," learning one root will help students remember the entire group.
Read the dictionary. Develop a daily list of words that may be of interest and learn them. Make it fun. Pick words for the week that are of a certain theme and then write a story around that theme. Develop writing skills that will enhance the newly learned vocabulary.