Feedback is essential to our development as a professional and as a human being. So why is it so painful to give and receive? Perhaps my tips could help you to give feedback that works:

Give it often
When feedback is reserved for annual reviews, people rarely receive it well. Give feedback regularly. You will be more practiced, and your people will be more accustomed to hearing it.

Be specific and, of course, constructive
Identify the specific behavior that a person needs to change. State clearly what you want him/her to do differently. You may use illustrated examples that help the receiver understand exactly what you mean.

Don’t forget to give praise 
Don’t forget to give earned and specific praise, as often, as you have a reason to do so. Giving praise, as giving feedback, is a precious gift and a win-win for both of you.