It is always advisable to purchase avocados which are still on the firm side as ripe ones will have their flesh bruised very easily. Avocados will ripe in just a few days if left at room temperature but the process can be quickened by putting them together with a banana in a roomy paper bag and leaving them in a warm place. You will know they are riped when they 'give' all over to a slight pressure and feel especially yielding at the stem end. Store ripe avocados in the salad drawer of the refrigerator if you want to keep them for a few days.
** Asian Online Recipes