Reading in a foreign language will reinforce your vocabulary in that language, provided you take the time to look up the definitions of words you don't completely understand. Read newspaper and magazine articles in the language you are learning, and have a dictionary by your side as you read. Read books and blogs using the same technique.
Writing in a foreign language is a great way of reinforcing your foreign language vocabulary. Any type of writing will suffice for this exercise, as long as the diction used in the genre is not so technical that you will need to look up every word. To practice this exercise, simply write something in your second language, and ask your language teacher to look over the essay and point out any vocabulary mistakes you made. Write in the language daily, in everything from grocery lists to notes and letters.
According to Concordia Language Villages, immersion in a foreign country is the best way to learn a foreign language. However, you do not need to physically leave your country to become immersed in a foreign language. Instead, you can just spend a few hours every day surrounded by the foreign language. Find podcasts on the Free Language directory in the foreign language you are learning and use instant messenger or skype to converse with pen pals in the foreign language. Watch DVDs, TV shows and online video clips in your chosen language.
Games have always been a staple of second language education. Get a partner who is proficient in the foreign language to give you clues as to the definition of a word. If you guess the word correctly in three tries, you get a point; if not, you lose a point. Another example of a game based activity is to play any conventional board game in its foreign-language edition.