Ask HN: How do you show appreciation?

After getting a particularly well timed and well intentioned email that made my day a while back I've started to proactively seek ways to show appreciation to others. Not flattery, but taking the time to call out the folks that really make a difference in my life and work. I now have a daily task to "Write an email that makes someone's days!". But I'd love to hear other ideas. What have you found effective in showing appreciation?