Ripe avocados that are soft, but not hard are the main ingredient in guacamole. Make sure the avocado is soft to touch, not mushy or brown and does not contain strings. If it is stringy and brown then the avocado is bad and needs to be discarded. If the avocado is too hard it will not separate from the skin and will also not mash together well. For any guacamole recipe, ripe is best, but not too ripe!