Some signs of alcohol use are: distorted vision, hearing, and coordination, mood swings, impaired judgment, and hangovers. Long-term effects are loss of appetite, stomach ailments, skin problems, sexual impotence, liver and heart damage, and memory loss.
The main reason not to abuse alcohol is the way it makes your family and friends feel. You just have to think about what you're going to put them through and how it isn't worth it.
Another thing is alcohol just doesn't effect you for one day. A heavy night of drinking can effect your decision making for up to 30 days. About 300,000 college students will end up dying due to alcohol related diseases. Also about 159,000 college students will drop out this year due to alcohol use.
In my opinion excessive alcohol consumption is asking for trouble. Although it might be "fun", you have to think what could happen to you (die, sick, make a bad decision) and how the next morning is going to feel. It's just not worth it.