example: "Hey, since you are also healing you might want to lay off the DPS so you don't pull too much aggro."
Negative criticism offers no sugggestions for improvement and is said in a negative and unsupportive way. Nothing makes most people bristle more quickly than unfair, unskillful, or unsolicited criticism. Very little productivity will result when team members feel unskillful.
example: "Argh! Learn how to tank more than one target! On every pull, I end up tanking!"
Lets all remember this little lesson and treat our fellow players with respect. We were all n00bs once and with a little patience and teaching, can get closer to uberness.
Thanks for reading and happy questing.