Tune in to "American Idol" and watch how Simon critiques the contestants. Simon doesn't sugarcoat any of his opinions and whatever is on his mind, he isn't hesitant to say. Pick up what he says and try to do the same when you have an opinion on someone.
Be witty and make people laugh. You can't be boring and stiff so throw in a couple of sly remarks without cracking a smile. One memorable comment Simon made about one contestant was telling him that his performance was like watching "Motown on Ice." If you can be bold and make people laugh at the same time, you will be loved.
Avoid being rude just for the sake of it. If you really feel someone can improve better at what they are doing or whatever they're wearing, tell them your brutal opinion and start off by saying "I don't mean to be rude but..." or say you're offering them a little constructive criticism they could benefit from. Say whatever is on your mind and if the person is dressing like Michael Jackson circa 1982 or their singing is equivalent to someone performing in a half empty bar and no one cares to listen, let them know that.
Develop a very thick skin because you will surely need it. You can't throw insults at somebody without taking a hit yourself, so if someone makes a bold statement about you that is truthful just let their insults roll off your shoulders, think of a smart comeback, or give them a little smile and don't say a word.
See the reality of things, even if you come across as pessimistic. Gain the "tough-luck" attitude and remember, you can't please everyone.