A fun way to introduce describing words...

Put an object in a paper bag and call two children. Let one child put his / her hand inside the bag, feel the object and try to describe it (Don't let the child see the object). The other child should write the words said by the first child on the board.

Children really enjoy this activity. This way you will get lots of describing words on your board by the children themselves. You can continue this activity by changing the objects in the bag.