The book "Hands Off My Honey" by Jane Chapman is an amazing mentor text for word choice.
These lessons go along with the book.
Day one: show the picture (a page from the book). This works best if it is 'printed' into a smartboard file or on paper.
The kids suggest words that might be in the book, or tell you what they see.
Day two: read the story aloud under the document camera and discuss some of the big words that you hear.
Day three: chop up the page with all the big words and display them under the document camera, or just project the whole page as PDF. Ask kids if they know what any of the words mean (probably have to read the word outloud thoughtfully a few times). Reading the book again is always an option if they are stuck on too many words.
Day four: Go over the words again. Let each student chose one word to copy down on their paper, They should draw something that represents the word. Then they can write a sentence that uses the word. The word itself MUST be spelled correctly :)
There a two levels on the same sheet - half sheet. One has a bit more room to write. This can be chopped off :)
Day five: If the students would like to choose different words to write about they may. OR let them have a chance to bump of some of the writing they have done in the past, or write a new story or journal that uses a big, descriptive word.