Great question!! It's really great that you are wanting to get some college courses out of the way as it will free up your schedule to take classes that you want as well as saving you lots of money!! One great way to get some of those general education requirement classes out of the way is to take AP exams. If you school offers AP classes then you should for sure take some. If you score well enough on the exam (usually a 4 or 5) then many colleges will grant you credit, allow you to sign up for a more advanced course, or both!! I came to my university with a semester's worth of AP credit and this allowed me to not only study abroad, but I also managed to graduate a semester early!! You should be warned though that most colleges limit you to a certain number of AP credits that can be transferred as they do not want you coming in with 2 years worth of AP credit (means less money for them).
Also, you may be able to take some college classes during the summers in high school. This is another great way to get some college courses complete but you will have to pay some money to take these class. Also be sure that your college accepts these classes as this is not always the case.
I hope this helps and I wish you the best of luck!!
Austin recommends the following next steps: