There are some things which you think would just be clear to the majority of the internet saavy population. We hold these things to be self evident, easy, and completely obvious:
1) If your potential employers name is "Mr. Daniel Rather," you cannot start your email with "Yo, Mista D., I've heard great things about you." You can, however, kick yourself in the face if you've ever even started an email to a friend that way.
2) Your potential employer does not care if you happened to be making a winky face while you are writing him or her an email. In certain settings this may even be construed as offensive. ex: "Wow Mr. X, you really nailed Mr. Q during that presentation last night, maybe we should discuss it more later! ;-)
3) Though AOL is the creater of the most popular instant messaging program, using repeated LOL's in your resume will not impress them when you look for a job. I promise.
Remember back in the old days when a bad record or a certain misdeed could get you blacklisted from the entire working community? Keep that in mind when writing a professional email...no one wants to hire someone whose only skill is Instant Messaging.
"But I'm profficent in both AIM and ICQ!!! LOL!!11" will only get you so far. Also, don't underline or italicize words you dolt, not everyone reads the way you think.