Search for a list of vocabulary words online. Typing in "free SAT vocabulary words" into a search engine will give you a plethora of options. Even if you do not plan to take a Scholastic Assessment Test, you can still use an online SAT list to learn important new words.
Once you find a list, write down the words you want to learn that day on the blank sides of several index cards and the definition on the side with lines. Post the words around your house or apartment so that you see them frequently. Make sure you look at the definition if you pass a word whose definition you don't remember. Take down the word once you've mastered it.
In a search engine, type in "vocabulary games." Playing vocabulary games online will help you to learn vocabulary in a fun and rewarding way. For example, FreeRice.com is a website that will donate rice around the world for every word you get correct in an electronic vocabulary quiz. FreeRice.com even has an audio function that will pronounce words for you as you try to figure out their meaning. In addition to online vocabulary quizzes, you can also play vocabulary games like hangman online.
Read a book online. Project Gutenberg is one website that will allow you to read many classic books online for free. While learning vocabulary through isolated words and definitions may seem efficient, reading a book will allow you to see those words applied in context. When you get to a word that you don't know, look up the word and write down its definition on your note cards. If reading is difficult for you, you can also find many books online in audio format.