The best way to “show” due diligence is with no surprises.
Due diligence is an in-depth review of all potential issues in an investment, acquisition, etc.
The best approach here is to make sure all material issues are aired before due diligence. Don’t hide the ball. Don’t wait for issues to blow up on you later. This just makes everything worse.
Put differently, make sure all the issues, even minor ones, are known to your investor/acquirer/etc. at least two steps before formal due diligence commences.