Direct: for a powerful communication, speak directly to the person you appreciate. Yes, it might feel awkward having other people around while you look directly at the person and call him by name. But the recipient of this appreciation will experience himself being valued in a way that is energizing and sincere.
And we all need to know that what we do matters to others.
Example: "Honey, thanks for putting in the extra time to make this special meal."
Think back to last time you showed appreciation; how did you phrase it? Were you direct?
Adapted from the Seven Languages for Transformation: how we talk can change the way we work, by Lisa Lahey and Robert Kegan. (c) 2001 Jossey-Bass