Used to tell someone firmly that doing something would be wise — usually to keep them out of trouble. It almost always appears in one fixed shape: 'you would be well-advised to ...' (or 'you'd be well advised to ...'). What makes it interesting is the tone. On the surface it sounds gentle and polite, but it is often a warning with a hard edge underneath: 'You'd be well advised to read the contract before you sign' means 'read it, or you will regret this.' A boss, a lawyer, a police officer, or an angry teacher might use it. Because it sounds formal and a bit distant, it is common in writing — letters, official notices, newspaper editorials — and less common in relaxed conversation, where you would just say 'you should really...' or 'if I were you, I'd...'. There is a second, much rarer use, closer to the plain meaning of the parts: someone who received good advice was 'well advised' by their lawyers. If you meet that one you will know it by the 'by' that usually follows.