Some free ways to build a better vocabulary are noticing the words that are unfamiliar, reading interesting materials, looking up the meaning of the words in a dictionary and reviewing the words. People should work on the vocabulary regularly, for a short period of time every day or every other day.
A larger vocabulary gives people an opportunity to understand a wider range of written and spoken texts. A better vocabulary also means that a person can express his thoughts better and have a better chance of affecting other people's thinking.
To start building a better vocabulary, carry a piece of paper and write down new words on it. To the right of the word column, draw two more columns. There are free dictionaries available online, for instance, Merriam Webster. Look the meaning of a word in the dictionary and write it down in the second column. Write down an example of a sentence with the new word in the third column.
Play dictionary games with friends. Ask teachers and instructors for the meaning of the words they use. Learn some common Greek and Latin roots, prefixes and suffixes that constitute parts of many English words. This will make the meaning of some unfamiliar words more clear.