Becoming a manager is a career milestone many of us strive to achieve. But being a manager is hardly a cakewalk, and the last thing you want to do is struggle early on in your new position. With that in mind, here are five blunders managers tend to fall victim to, and why you should avoid them at all costs.Your direct reports might have their own distinct talents, but they're not mind-readers, so if you don't make it clear what you expect from them performance-wise early on, they're likely to wind up disappointing you in one way or another.