Do you ask clients to initial your work?
A person's signature is extremely valuable. Getting a signature is hard work. Salespeople use all sorts of euphemisms to avoid that confronting request: "if you could just sign here..."
However, requesting a signature (or just an initial) on non-contractual type documents (especially screenshots, mockups, or data-schemas) is very beneficial.
When you ask a client to 'review this screen mock-up' they will generally take a cursory glance, perhaps make a comment or two and then move on to something else. Asking them to initial/sign the document always makes them take a second or third look, ask someone else, or at least spend a few more minutes working out whether it's correct or not.
Training clients to review the work carefully leads to better quality projects.