Learn by rote. Writing the words down repeatedly or using flash cards will strengthen your vocabulary retention. There are also free online services such as Quizlet and Flash Card Machine with pre-made flash card sets for many different languages.
Associate vocabulary words with English words or phrases. If a foreign word sounds similar to a word that you already know, use that as a mnemonic device: picture the similar-sounding English object in your head to remember the foreign vocabulary word.
Test yourself. Print out lists of the foreign vocabulary words and write the English definitions next to each entry. Correct your self-exam and work on remembering the vocabulary words that you got wrong.
Immerse yourself in the language. Join or start a language study group or attend social events where the foreign language is spoken. Watch movies with the audio track set to the language you’re studying.
Read. Head to your local library: they may have available books, magazines and newspapers in the language you’re studying. Being exposed to foreign language words in context will help vocabulary retention.
Invest in a language learning software suite. Many language learning programs focus on vocabulary retention using several of the above methods.