I once worked for a company that had no set job levels. This resulted in a flurry of people who aspired to management simply because it was the most visible career step. They saw management as power, not as a role that required a particular skill set. Here's what I used to ask staffers to consider before they set their sites on the management role.
Be prepared to deal with resentment on the part of your former colleagues. You know those guys you used to go have beers with after work? Well, a couple of them may have also applied for the job you got. Though they say they're happy for you, deep down inside they think they could do a better job than you. Also, as a manager, even if you still get invited to the afterwork forays, remember that you can no longer partake in the gang's favorite pastime--office gossip. You have to rise above that and your buddies may not be comfortable with the change.
Be prepared to deal with whiny babies and uncomfortable situations. Person A doesn't like the volume of Person B's voice. Person C thinks Person D has a body odor problem. It may surprise you to find out how common situations like these can be. And guess who has to take care of it? The manager. You can tell your employees to speak to each other if there is a problem, but there will be a great reluctance to do so. They'll say that's what you're there for. If you're not comfortable telling your employee to take more frequent baths, you might want to stay out of personnel management.
Be prepared to ask your team to do something they may be neither prepared nor staffed for simply because upper management has asked you too. If you can't do this, be prepared to be cast in an unfavorable light by upper management. You don't have to adopt either extreme--lapdog or rebel--but know that walking the line in between can sometimes be as tense as walking a tightrope and is neverending.
Be prepared to fire someone. And know that even though you have reams of documentation for doing so, it's an altogether different ballgame when you have to look that person in the face and tell her she's fired. Aside from Donald Trump, I don't think any real person likes firing someone. A colleague of mine once had to fire a staffer who had a personnel file so thick with write-ups and probationary notes you could fill a mini-van with it. She was still shocked at the final outcome and proceeded to cry and beg for a reprieve.
Be prepared to tell a long-time employee why someone with less seniority was promoted over him. Dedication is good, but longevity alone should never be the sole reason for promotion. Talent and initiative must be rewarded where it is found.
Be prepared to have your every opinion and course of action questioned by the team malcontent. Seriously consider his suggestions but stick to your guns if you know, for reasons he may not be privy to, that the course of action you've outlined MUST be taken. And be prepared to deal with this person in a disciplinary manner if necessary because chances are what he says out loud to you is only the tip of the iceberg of what he is saying to the rest of your staff.
Anybody got any other suggestions?