Having a higher vocabulary will help you convey your thoughts better to other people. There are other advantages from seeming smarter and more interesting to other people. Most people know about the thesaurus which is probably the best way to increase your vocabulary, but that is boring. There are some slightly more entertaining alternatives, some of which I am sure you haven't thought of.
Word games are quite possibly the most fun you can have while also expanding your vocabulary. They can be anything from word searches to crossword puzzles. You should start with some easy stuff and work your way up, however, if you keep things too easy forever then you won't learn anything. Always keep a dictionary close by as well so that you can search for the proper word and learn what it means.
Word of the Day
Lots of people swear by this method in which you choose a word for the day and try to use it whenever possible. This gives you a chance to use it, which helps reinforce what you learned. This also gives you a chance to impress other people with what you learned. This isn't going to really help you at all but it's a plus.
There are some calendars which come with a nice word of the day line on them. It comes with the definition and everything. These are great for in your office and takes the pressure from finding the word yourself. Alternatively you can use Websters website for a word of the day! Whichever is most convenient for you.
Read More Books
You can learn plenty of brand new words while reading some of your favorite books. It is best to keep a dictionary around at all times so that you can look up the real meaning of these new words that you learned. If you like to take your books out of the house though then lugging around a massive dictionary is probably out of the question. Luckily you can get an electronic dictionary for cheap and it will work just as well. They make them small enough to fit right in your pocket.