Capitalizing on positive actions, experiences, and events to improve satisfaction, well-being and quality of relationships involves offering detailed, nuanced responses rather than the more common brief exclamation. Here are two types of situations and the recommended approach.
(1) When someone does something you appreciate, offer positive regard. (termed "ongoing regard" in Robert Kegan and Lisa Lahey How The Way We Talk Can Change The Way We Work, 2001)
More powerful positive effect is achieved by offering behaviorally specific information rather than a brief, general response--e.g. "I really appreciate the way you took the time before our meeting to summarize the key supporting data. That really facilitated our decision making." This is in contrast to the relatively common "You did a great job!"
The detail in the first response is likely to feel more thoughtful and genuine than the more vague and global "great job." Also, starting with "I" rather than "You" makes it feel more like the speaker is offering potentially valuable information from experience for the receiver to consider rather than conferring some form of judgment. The latter can subtly diminish any intended positive effect.
(2) When someone reports experiencing a positive event, respond in an active-constructive way. Such responses have been linked by research to increased well-being and relationship benefits such as increased commitment and trust. (Shelley T. Gable et al in Advances in Experimental Psychology Vol. 42, 195-257, 2010)
As with positive regard, benefits are achieved by going beyond the more usual brief exclamation (e.g. "That's great. Congratulations.") and asking questions about the event, seeking additional details, elaborating on the possible implications and benefits for the discloser, and commenting on why the event is meaningful to the discloser in particular. Such responses are also more powerful when accompanied by conveying emotions of interest, happiness, or pride. (Gable et al, 2010)