I think that a lot of us wonder about our vocabulary? If you can hang out with other writers, chances are you have nothing to worry about. You will be surrounded with great new words whenever the group gets together. But what if you are somewhat of a loner, like a lot of us tend to be. I'm thinking about incorporating some word games into your day... even if you just have ten minutes to spare... it might be the only play time you have, so take advantage.
*And always keep a dictionary and a thesaurus on your desk. I tend to grab mine a lot... much to my annoyance. "Why don't I know that word," I can be heard muttering under my breath? So there you go. If your vocabulary needs a little work, look for a fun way to do it!