It seems that whether their manager is "good" or "not good" plays an important role in whether my friends are "happy" in their jobs. Based on my work experiences, business school training, and just talking to many people, I will try to focus on what a good manager should do specifically for major tasks, and the key attributes he or she should have. This list is definitely not meant to be exhaustive, and I would be grateful if readers share their insights in the comment thread.

*What a good manager should do for major tasks:
1. Explain why and what to do. Be clear about how the task is related to the bigger picture and what the expectations and deliverables are.
2. Provide guidelines on how to do the task. Provide recommendations how certain tasks can be accomplished effectively and efficiently, but stress that these are only recommendations, and not rules.
3. Be clear of the timeline. Be upfront about the deadline, and provide context why the deadline is important. Do not "hedge" the deadline by forcing the direct reports to rush the work unnecessarily.
4. Share with them the support available. Inform them about the different resources available to complete the task, especially who to seek out for help if necessary. Set their expectations on your availability for this task.
5. Consequences if the task is not done on time at the right quality. Let your direct reports understand what will happen to them, you and the team if the task is not done on time at the required quality.
The initial conversation can be 15-20 minutes, which will prevent a lot of unnecessary communication down the road. This conversation should also be iterative as new information is received.

What attributes a good manager should have:
1. Genuine care for the development of their direct report. The good manager should be genuinely concerned about the direct reports' development in the company, assuming he or she want to make the effort to develop.
2. Refrain from micromanaging unless absolutely necessary. This is harder than it sounds. Many managers are promoted because of their individual contributions, and not necessarily because of their ability to manage. Therefore, some managers find it irresistible to be more directive than necessary to their direct reports who are not performing at the same level of excellence as what the managers were doing before promoted. When deciding to be more directive, a good manager has to balance the trade-off from the shorter term increase in quality of work produced vs. the longer term impact of lowering motivation of the direct reports.
3. Balance fairness and discretion. A manager has to treat all its direct reports in a consistent manner but yet be able to make exceptions for individuals with specific needs. Being able to strike the right balance is critical in gaining trust and avoiding favoritism.
4. Over communicate rather than under communicate. A manager should let his direct reports be aware of how the team's work contributes to the bigger picture, and communicate any update from senior management to the direct reports accurately and promptly. The manager should realize the more context the direct reports have, the more flexible and effective the direct reports will be in executing their tasks as they are closest to the actual work.

* I learn this from my first project manager