Ask HN: How to properly "underpromise and overdeliver" in job interviews?

Of course, the approach to sell your skills at the right value is the ideal approach, but I am not experienced enough to know exactly where my value is skills-wise. So between erring on overselling or underselling, I always choose underselling.

I want to underpromise and overdeliver, but I also need to get job offers so I don't want to let employers down too much with the "underpromise" part. How to find the right balance? I have to be humble without losing my chance to someone who will oversell their qualifications.