Doing well in college

It is well known that many students do not do well in college. This can happen for a million reasons. It can happen even if you did really well in high school, and it can happen in some courses and not others. I can't go into all of the possibilities here, that would be a whole book. What I will do is mention a few things that seem to be common.

1. College requires deeper understanding. In high school, it is often enough to learn the facts. In college, you will be expected to apply ideas to new situations, to create new problems, etc. Educators often refer to "Bloom's Taxonomy." this is a hierarchical list of levels of understanding. In High school, understanding at the lowest level (knowledge) is often enough. College calls for higher levels (comprehension, application, analysis...).
2. College takes way more time than high school. The number of hours of homework per week in a college course is usually two or three times its number of credit hours. Often it is more. In 251, you should expect to spend 10 or more hours on homework each week.
3. College requires you to be your own boss. For instance, college courses often require that you learn material that is in an assigned reading but is never discussed in class, or something that the professor mentions in class, but which is not in any assignment. Similarly, to graduate from college, you may have to satisfy requirements that vary from major to major and from year to year. You are responsible for finding out what these are. There are many other examples, and it is not worth listing them all. The bottom line is, you must constantly be asking yourself "what could be expected of me?" rather than waiting for instructors or advisors to tell you.
4. College requires you to learn things for good. That is, when you take an engineering course your senior year, your professor can and will expect you to use all the skills you learned in your freshman year writing course, your high school geometry course, your sophmore year physics course, etc. If you decide to learn something well enough to pass the next test, but not well enough to remember it a year later, you are taking a $180/credit hour gamble with your own future.