There’s no such thing, according to Edith Zimmerman:
After editing an advice column for two years, I’ve decided that there is no such thing as advice. There are only problems and the ways people handle them. Advice, on the other hand, is when you hear a description of someone else’s problem and then tell the person something about yourself. Hopefully whatever you say is funny or interesting, but it has little to do with actually helping anyone. It may seem or feel like it does, but there are always more variables than we’ll ever be able to see or understand, and best case scenario you’re pressing on the problem a little bit in a way that engages the problem-haver.
Maria Bustillos approaches the quandary from a different angle:
Anybody who supposes himself wise is already demonstrating the reverse. Therefore the cleverest, most beneficial advice must always come disguised as something else. Because who can ever really believe that he knows better?