How to give a compliment that sticks around

Back in college, a friend of mine who was studying theater mentioned that when he would see a play, he'd make a point afterwards to compliment the actors on details about their performance, instead of just saying, "Great show!" or "Good job!" By expressing an original thought, you demonstrate your sincerity. And your feedback is more likely to be remembered.

Here are a couple compliments I've recently gotten from friends, which will stick with me because of their originality:

"I wish I could put your sense of reason in a bottle and serve it to people."

"Never have I seen someone so opinionated try so hard to diffuse his own opinions."

It took me a while to be sure the latter comment was even a compliment.