it's the gentle squeeze test I'm afraid - if you feel your fingers make a little indent - they're just right. If your finger feels like it's about to penetrate to the core- use only for guacomale. Trick to speed up the process of ripening the avo is to put it in a brown paper bag with a banana. Yes, this does really work - it's a chemistry thing, something to do with the ?potassium? that bananas' emit apparently (thought could be wrong on exacly what it is they're emitting!)