Laughing in my head (instead of LOL. When you AIM the person sitting next to you at work "LOL", but they can clearly hear that you are notlaughing out loud.)
Suzy: Did you see what Mary is wearing today? What, did she get come in straight from her side job at the strip club?
the correct way to let someone know you find what they say amusing. Instead of say lol (laughing out loud) say limh (laughing in my head). In reality you know you are notlaughing out loud but in fact laughing in your head.