Criticism

This is a very helpful link on criticism by Mark Dever. His five main points are to give criticism...

1. Directly, not indirectly.

2. Seriously, not humorously.

3. As if it's important, not casually.

4. Privately, not publicly.

5. Out of love for them, not to express your feeling or frustration.

In the comments, there is additional information on the pros and cons of e-mail criticism. It's great stuff.