Well-known author and lifestyle design guru Tim Ferriss has a lot of experience giving, taking, and rejecting advice on a variety of topics. Over the years, he’s developed a tried-and-true method for telling good advice from bad. Ferriss has learned to reject advice that cannot be tested, usually because it is too vague and nebulous to lend itself to proper experimentation. If advice can be tested with repeatable results, take it, Ferriss said. Otherwise, reject it as more slogan than actual advice.