I don't know the first thing about preparing for college; Help!?

I just finished the 8th grade, and in the fall I will be attending a dual enrollment school. If I complete the requirements and graduate, I could have my diploma and my Associate's by the time I'm 17. The problem is, I don't really have a lot planned out after that. Actually that may be an understatement. I don't even know what career field I want to pursue. All I know is the college I want to attend. I'm a well-rounded person, so I have a lot of interests. I can't decide on what I want my major/occupation to be. I also don't know how to prepare for college after high school. What can I do to decide what I want my career to be, and also, what can I do to start planning for college? Thanks.