Now you know that the data stored in the “deep web” is mostly harmless. And it’s actually good that they are stored “in depth”, remaining invisible to those to whom they are not intended. But if some of them, such as corporate correspondence, “surface” and get into the search index, then trouble may begin. Therefore, it is better to properly protect your piece of “depth” — accounts and documents to which you have access.
Use strong and unique passwords. And if there are too many accounts for you to remember them all, a password manager will help you.
Before entering credentials, always check where exactly you are going to do it. For example, if the address of a page is written with an error or, say, looks like a meaningless set of letters and numbers, this is a sure sign that it should not be trusted.
Give access to confidential documents only to those who need it.
Do not wander around the dark web if you are not sure that you can distinguish a human rights defenders forum from a hacker one. You never know who you can run into there.
And use reliable protection — it will save you from a whole list of troubles that can happen online.