As you read your students' papers, you will come across several compositions that use higher level vocabulary instead of the easy to write, low level words. Each time you find one of these words, and it is used correctly in context, the student has passed the part of
vocabulary that has to do with application. For these students, you can use the idea of extrinsic motivation by writing their names on the back of tickets and placing them inside the "Word Bank". Every week or so, have a raffle and give some sort of prize to the students whose names you pull out of the bank. (whatever is appropriate for your class). After just a few weeks, you will notice a tremendous increase in the amount of higher vocabulary that they are choosing.
A caution here is to be sure the words make sense and fit where they're placed. In my own classroom, I also gave out bonus tickets for the first person quiet, for homework completed, or any other important classroom procedure that students were following, or things I wanted to reinforce as a teacher.
~Bill MacDonald, The Writing Doctor