From Robert Cialdini:
Ask your boss for advice concerning your planned work, not for opinions or expectations regarding it. It turns out that evaluators who are asked to provide advice (versus opinions or expectations) on a plan are put in a cooperative state of mind before they even experience the plan, which makes them more favorable to it when they then do encounter it. There’s a saying, “When we ask for advice, we are usually looking for an accomplice.” I’d only add on the basis of scientific evidence that, if we get that advice, we usually get that accomplice. And what better abettor to have on a project than someone in charge?