lol is smiling, LMAO is a chuckle, ROFL is laughing
I add lol to the end of most of my instant messages or PMs or whatever to try and show that I'm kidding, my brand of sarcasm and irony is OFTEN misunderstood in text. Hard to show inflection when you type. On the forum I try and add some kind of smiley to portray the same thing.
lol = huge smile 100% of the time, with a smile 90% of the time
LOL = average laugh, but finding it funny
LOL!!!!!!! = I'm laughing really hard, maybe eye water a little
LMAO! LOL!! OMG OMG THATS HILARIOUS = I've read your post about 20 times, kept laughing, eyes watering, it will never get old and you made my week.