This seems a little bit of an odd topic to be making. I usually browse around the dictionary for fun (strange) to find a word I can incorporate into my writing, but I never get how to. I mean, I understand the sentence, but I can't make the word feel right with what I'm saying.
I would almost thing a Thesaurus would be more helpful in this case. Taking some of the words you use frequently, then looking up new words to take their place to add of bit of spice that way. Since you already basically know the setting in which they can be applied.
The best way to truly improve your vocabulary is to read a lot of writing. That will incorporate the word into your vocab not through blunt memorization, but through examples. I find if I read a word in the context of a book and encounter it a few times there, it's so much more likely to become used than if I encounter it in a dictionary.
The danger there is that not everyone uses a word correctly. How many times have you heard someone use the word "literally" simply for emphasis? Or read that someone is "loosing" his or her way. The same is even more true when writers pull up new words and use them in writing. The writer may misunderstand the definition, or get the conniotation wrong (look up the difference between connotation and denotation). I always have a dictionary or two handy when I'm writing, as well as online dictionary links in my browser's favorites. And yes, I also use a thesaurus, but I always go back to the dictionary if the word I select is not one I know well. I also like to have a dictionary handy when I'm reading. If an author uses a word I'm unfamiliar with, I look it up. Sometimes I just ponder a word, and want to know it's origins, so I look up the etymology of the word, if it is given.
I like to have a dictionary at my side while I read, but sometimes I'm just lazy and don't look it up. Ergo, the dictionary lies there and does nothing for me. I'm more inclined to look up words that look odd - i.e. have odd spellings. I probably do that for two reasons: I can remember the meaning of an odd-looking word, and I can - I know I shouldn't - impress people with it at a later date. I also like to use foreign words/phrases in my writing. Perhaps not so much so in my fiction - it can be cumbersome - but in research papers, summaries, or analyses, I think that foreign words/phrases add flare. A caveat: figure out early on if your instructor has a predilection for foreign/peculiar words, for if not, you must avoid them.
