One of the simplest ways to improve vocabulary is through repetition. Keep a list of words you want to learn, record their definitions and go over the list daily. Once a word is mastered, wait an extra week before crossing it off; over-rehearsing the word ensures that it's not easily forgotten. Fit these words into your conversations and thoughts to further familiarize yourself with them.
Elaboration is the process of linking a word to relevant information at the time it's learned. Link the vocabulary word to concepts that are meaningful to you, such as similar words, examples, synonyms and other concepts to which you can relate. One method of elaboration is learning usage examples. When learning a new word, try to read as many usage examples as possible; say the examples out loud, think about them and visualize the usage situation in your mind. Learning related words, such as synonyms and antonyms, is also a useful elaboration tool.
Reading on a wide variety of topics is a great way to improve vocabulary. However, many people skip over words that are unfamiliar to them and come away with an incomplete understanding of the word. When you're reading, record any unknown words and try to figure out their meaning through sentence context; this gets you thinking about the words. It's important to also look the words up so you have an accurate meaning. Keep these words and their definitions in a list that you look at until you're comfortable with them.
Making a word personally relevant increases the chances you'll remember it later on. When you learn a new vocabulary word, think of examples from your own life where applies. For example, since "belligerent" means "aggressive and war-like," you could think about your belligerent relative who makes aggressive comments at family functions. When discussing him, using the word "belligerent" helps seal the meaning in your mind. Another way to apply personal relevance is to define the word in your own terms after you've looked it up. After reading the definition for "belligerent," you could adjust it to "my relative who makes aggressive remarks and is ready for a battle."
In addition to being fun, playing traditional word games with others increases your exposure to unfamiliar words. When playing word games, a dictionary is often on-hand to look up words that are unknown to one or more players. Seeing the word used in a game and hearing its definition makes it likely you'll remember it later on. Games like Scrabble, Boggle and crossword puzzles can all help build vocabulary.