Despite HR Department is the one that handles the employees’s work related issues and matters, but from the other side there are few things and rules might not be clear for employees, and HR won’t clarify that.
As per Wall Street Journal, there are 10 things you should be aware of ,and HR won’t tell you about:

1. "We're squeezed too." There was a time when human resources departments handled every staffing need at a company, from hiring and firing to administering benefits and determining salaries. But HR's role has begun to change significantly as departments have shrunk at companies across the board. According to a study by the Society for Human Resource Management, the profession's largest association, the head count at the average HR department fell from 13 in 2007 to nine in 2008. "HR departments are under pressure like never before," says Steve Miranda, the society's global HR and integration officer.

2. "We're not always your advocate..." Employees often turn to HR if they're having problems with a manager, but they don't always come away satisfied. You cannot take in consideration what all said by HR.

3. "...but we can help your career." Human resources managers do much more than handle employment agreements, medical forms and paperwork. They can also have a hand in helping to retain and promote top talent. Employees often want to avoid HR …, "but you really should do the opposite."
One way to be recognized for your work is to keep human resources in the loop, by sending your HR manager an occasional e-mail to let her know how you've been contributing to the company's success. That kind of connection could help land you a promotion when positions open up or even keep you off the chopping block during the next round of layoffs.
4. "Want the job? Then you'll want to get to know us." With unemployment hovering around 10%, HR managers are inundated with responses for every job posting. In fact, some companies are hiring outside firms to post jobs and sort through résumés, presenting only a dozen or so qualified candidates for consideration.
How to make the cut? Be sure your résumé and cover letter highlight the skills asked for in the job posting; HR tosses applications that don't meet all the basic criteria. And ask yourself what in your background fits the company's needs, says Mike Wright, senior vice president of outsourcing sales with Hewitt Associates. "You really need to sell them on your abilities,"
5. "Yes, some public sites like Facebook can get you fired."
Employees like to think that what they do on their own time is their own business, but that's not always the case. According to a 2009 survey by the American Management Association and the ePolicy Institute, 27% of companies have policies about what employees can post on personal blogs. "You have to think about whether this will come back to haunt you,"
6. "In some companies, we're not very useful at all."
It seems that every company has a different approach to human resources. For some, it's nothing more than an administrative job, involved with hiring and firing, benefits and not much more. These firms may have a dysfunctional work environment with high turnover, where employees can often feel trapped. By contrast, companies with strong HR departments have been shown to do better financially. Empowered human resources reps can also help guide employees through their careers.
How to tell the difference? For one, see whom HR reports to. If it's the CEO, that's good. If HR managers are in the field, getting to know employees and how the company works, that can be another key, an employee-relations panel member with the Society of Human Resource Management. One way to suss out a human resources department's effectiveness is to ask the manager interviewing you how HR operates and what it has done to help her achieve her goals. If she doesn't have an answer, it's "not a good sign,"
7. "You're not paranoid—we are watching you."
Companies want to make sure you're working most of the time, not sending joke e-mails to your buddies. Half of organizations in the ePolicy Institute survey banned the use of personal e-mail on the job, and more than one in four reported firing employees for misusing the Internet. In many companies, HR works with the information-technology department and the legal team to develop policies for electronic communication.
Many companies employ software that sifts through e-mail looking for curse words or sexually explicit language. IT monitors Web usage and can see every site an employee visits. In fact, anything you do via the company's server—most activity on an office computer, including personal e-mail—is subject to review by your boss. Firings over these issues are on the rise.
8. "Read the fine print."
When you take a job, you may be agreeing to more than you know. In the fine print of employment agreements, employee handbooks and job applications, many companies include a mandatory arbitration clause—meaning that you agree to give up your right to take any dispute to court, even if the employer has broken the law.
9. "We know more about you than you think."
These days companies do a lot more than look over a pile of résumés and call a few references before hiring a new employee. They bring in outside firms to dig into an applicant's background and verify education and employment histories, and they will often even search criminal records and credit reports. According to a survey by the Society for Human Resource Management, 53% of companies have conducted credit checks on their employees. Companies are concerned that "if you have a lot of financial pressure, you might not act in the best interest of the company,"
But not everyone thinks such measures are extreme. If anything, employers don't dig deeply enough, so an employee with a problem with a previous employer or criminal record will try to hide it.
10. "We love tests."
Job seekers today have so much experience packaging themselves, with tailored résumés and rehearsed answers, that companies turn to tests to find out more about what makes them tick. A 2009 survey by research firm IOMA found that 26% of companies conducted personality, psychological or integrity tests on applicants. Job seekers may also be asked to take a test to quantify their creativity. What's more, insurance companies are pushing businesses to screen for traits like risk-taking, a quality the underwriter would not appreciate in, say, an applicant for a forklift-driver position.
Hence after seeing above what could be a “risk” for employee or job seeker, some precautions should be taken ahead to avoid such tricks. However, instead of letting your emotions take over your open-mindedness, ask yourself these ten questions:
  1. How valuable am I to the organization?
  2. How have I communicated that value to the organization’s leaders?
  3. How have I communicated that value to the organization’s employees?
  4. What measures am I using to determine success?
  5. How are the HR programs aligned with the goals of the organization?
  6. Do I advocate for employees fairly and consistently?
  7. Do I know how to balance the competing interests in the organization to provide a fair viewpoint?
  8. Do I clearly communicate the reason behind my position to employees, managers, and company leaders?
  9. Am I an example to those within and around the organization of its key values?
  10. What can I do today to serve my customers?