And don't think grades aren't important. Without good high school grades, you won't get into the better colleges. Without good college grades, you won't get the better jobs. It's not going to happen. Show up at every class.
Poor attendance is a sure way to miss important information.
In college, it's very easy to not attend classes. Force yourself to never miss a lecture. Have a separate notebook for each class. This will help you stay organized. Take notes carefully.