Preheat oven at 350. Prepare a baking sheet with cooking spray. In a mixing bowl, combine margarine, egg whites, and vanilla. In another mixing bowl, combine flour, sugar, and salt. Mix wet ingredients with dry ingredients just until moistened. Spoon dough into a cookie press fitted template of desired shape. Press cookies 2" apart onto prepared baking sheet. Bake 10 to 12 minutes, or until golden brown.