Unnecessary employee turnover results in significant costs to employers. According to a report from the Center for American Progress [PDF], when an employee leaves a job, it costs an organization about 20 percent of his or her annual salary to recruit someone new. AARP notes that potential indirect costs of turnover include lower employee morale, formal and informal training for new hires, advertising and promotional materials, referral bonuses, relocation expenses, and background checks. Not to mention that your other employees are burdened with additional work while you fill the empty position.

Research shows that more than one-fifth of turnover happens in an employee's first three weeks on the job. If employees are leaving early on, it means your organization is making a poor first impression. According to the Society for Human Resource Management (SHRM) [login required], employees are 69 percent more likely to stay at an organization with an efficient onboarding process.

One problem is the misinterpretation of orientation as onboarding. Distributing company literature and having the new employee sign up for benefits are an important component of onboarding, but it's broader than that. Onboarding is integrating employees into the organizational culture and helping them understand the organization's values and processes.

Colleagues are the number-one factor in employee happiness. So it just makes sense for onboarding to start with people.

As in life, first impressions are important. The new employee has made a good first impression on you—that's why you hired him or her. Now it's time for your organization to do the same. Here are five tips for optimizing your onboarding process.

Introduce new employees to their teammates. Research by the employee engagement firm TINYPulse found that colleagues are the number-one factor in employee happiness. So it just makes sense for onboarding to start with people. Be sure your new employees meet colleagues in departments other than their own. Some organizations use creative methods, such as a scavenger hunt, to get new hires out into other parts of the workplace.

Be prepared. Nothing reflects more poorly on an employer than a lack of organization on the first day. New employees will think you don't value their work. They may slack off or pursue another job opportunity. To avoid this, be sure to have someone at the front door to greet new employees on arrival. Have their workstations set up and all the relevant paperwork ready to go. Demonstrate that the sooner they're able to do their job, the better off the organization will be.

Provide valuable feedback. One of the most important things a manager can do for a new employee is to offer feedback. Expect that new employees will be on a learning curve—they won't be able to do the job as well as a veteran in a matter of a few days. Praise new employees when they do well and offer guidance on how to do better. Regular, supportive feedback is critical for all employees, but especially newbies. If they hear nothing for several weeks and then receive a poor evaluation, you can bet they will have one foot out the door.

Offer mentorship. New employees in mentorship programs are more likely to be knowledgeable about their new organization and embrace its values, according to a SHRM study [login required]. Veteran employees have institutional knowledge that new employees don't. They know the organization's informal processes, they know how to prioritize projects, and they know the personalities in the workplace. Trust them to provide guidance to new employees.

Ensure consistency with remote workers. Onboarding is important for all employees—including those you hire to work remotely. TINYpulse research found that remote workers are more productive and happier at work, but they have poorer relationships with their coworkers. One persistent issue is communication. It's management's responsibility to ensure open, frequent communication between workplace employees and remote workers, starting on day one.

Onboarding isn't a "set it and forget it" task. Employers that succeed at onboarding are constantly updating and tweaking their systems to reflect how the organization has changed. And they're reducing costly turnover because of it.