Most of my students love words. I encourage them to keep a list of words they love, not just for the meaning, but for the sound of the word itself or for the feeling they have when they speak or hear the word.
I am a firm believer in ten new words a week. This is an old-fashioned idea and I believe the reason it has persisted long enough to become old fashioned is because it is tried and true. In other words, it works.
When homeschooling my own daughter, I assigned ten new vocabulary words each week. I had her look them up in a dictionary (the actual book, not the online tool). She would then write out each definition. She would memorize the spelling and definition of each word. The next night she would write three sentences using each word and by the end of the week, she would write a short story or poem using each vocabulary word. Each week, I would create a test on spelling, meaning, and usage. I found this to be an excellent way to help her build her vocabulary. Why not try this with your child?
In addition, I highly recommend Wordly Wise books and online tools. http://www.wordlywise3000.com/