Consider a few quick pearls that will increase your success at giving valuable feedback:
Realize that learners (students/residents) crave feedback....proven in multiple studies
Feedback IS a powerful teaching tool and isn't just a way of evaluating someone.
Avoid at all cost, the phrase,"good job." Be specific about what you mean
Praise in public, perfect in private
Avoid the "complain syndrome" and don't fall victim to it. This refers to the phenomenon in which we complain about a behavior or trait and NEVER actuall tell the person. We have all done it. Set yourself apart from others by giving the learner the needed feedback.
Learners won't improve without feedback. Just like the Nike commercial says,"Just do it!"