Trying to figure out what career you want to pursue depends all on what makes you happy and what you are good at. If you are analytical, accounting, law or research could be something to look into. If you want to help others the medical field might interest you. If you are independent, entrepreneurship might be something that you are interested in.
Also you can take career personality test surveys that describes what you could do for a career could be of value to you in deciding what field to go into. The test gives you a breakdown of which type of career you would be good at.
Doing some type of internship might help you too. This could be in business, medical or even administration. This would could also be an indicator of what you DON'T want to do for a career.
And lastly what subjects were you good at in high school and what do you want to pursue. This would be a good indicator of what would make you happy at work.
Pick a few schools that you would like to go to after reading about them on one of the websites on colleges or their websites. Make sure to include a safe school or two and a "reach" school. Visit as many as possible. Think about the weather, the size of the school both physically and in terms of the number of students, about whether it's in a city or in the outskirts, if it's in the city is it a campus or just buildings scattered throughout a section of the city (or the whole city), will you be comfortable going out at night if you eventually live off campus (or go off campus at night), and how/where are the freshman dorms (try to see them when visiting). Add anything that matters to you to the list. It may seem like a lot but you'll spend four years there and you want it to be a good experience. Once you've further narrowed down your list of school's apply to the ones you liked. Make sure to include several schools besides your first choice, again some should be in each category.
As for major what has been previously said is correct. Apply undecided or to the school of Arts and Sciences. That will let you take a variety of classes. You probably do not need to declare a major until either late in your sophomore or mid-junior year.
Do well this year (don't slack off because you're a senior!) to help your junior-senior GPA. Enjoy the fun parts of senior year. Much success in college and beyond!