Gently press against the skin of the avocados. If they feel firm, then they are not yet ripe. If they are slightly soft when pressed, it means they are ripe and ready to use. If you go shopping over the weekend, but plan to use avocados during the weekdays, then buy unripe avocados. Wrap each avocado individually in a newspaper or paper bag or kitchen towel and let it ripen at room temperature for two or three days.