A best practice in performance management is definitely to get a complete review of your employees by utilizing feedback from themselves, from their peers, from their clients, as well as yourself as management. It's definitely not an easy process to engage in, and dependent on how big your organization/department is, it can be a very arduous task taking careful coordination and constant reminders. While anonymous information is best, it too can be skewed. Building your organization up to provide such intricate and a total 360 review of staff can take months, teaching soft skills and ensuring that giving and receving feedback is done so in manner that is respectful. While feedback is a gift, it's not always perceived that way.
The one recommendation I do make however, is to always get feedback from a self-evaluation point of view before writing the performance review for the employee. This allows you as the manager to do the following:
1.) You can see if you're actually in alignment with your employees - you can assess to see if they have actually taken cues from your feedback throughout the year and incorporate it into their own self-evaluations.
2.) You can prepare for the interview better, knowing examples they have used and incorporating such ideas into the final performance review. Working collaboratively will make the process easier, more enjoyable, and gives management great clues into where they need to step up their game in terms of giving feedback throughout the year.
I've had a few managers struggle with this process - but given the alternative, which is walking in cold into a performance review interview, not knowing what your employees are really thinking about their performance - now that's a scary thought! Getting them involved in the process is truly a great way to start your feedback process!