Effectively delivering constructive criticism can be simplified by remembering the “hamburger rule,” and Nate’s Productivity Tips weblog introduces this timeless classic.
When offering a critique, you begin with a constructive compliment on something the person does well (Otherwise known as the fluffy bun part). You then get to the meat of the matter, which of course is the constructive criticism part. Finally, you end with another constructive compliment (i.e. the other half of the fluffy bun).
Though I learned it as the “sandwich rule,” this practice is highly touted in most professional public speaking courses and very easy to remember.