Start with the basics - do you like to work with your hands or are you more inclined to follow what some people deem "professional" jobs (think computer programmer, accountant, etc.). There is NOTHING wrong with following either one of these career paths though some people will make you think it is all about the education. From answering this basic question, you can start to narrow down your goals. For example, if you like to work with your hands, now you might be looking at a vocation such as auto mechanic, plumber, electrician, etc. Again, there is nothing wrong with any of these (although yes, some people will look down at you - ignore them). Note that the idea of choosing a career is the same for both trades and professional. Here you start discarding careers - maybe you like to work with your hands but don't really care for working on cars, there goes auto mechanic. Maybe you like the idea of working on cars, just not on engines - think body man, metal fabrication, etc. (In case you didn't notice, I am specifically using trades, not just to show you how to choose but also that college is NOT necessary and is not right for everyone). Once you have narrowed your choice down to a few careers (maybe you do like auto mechanic AND body work, etc.)., look for a vocational school in your area AND talk to someone who actually does the work. You now have the basic info you need - now go to a local jobs center AND talk to that vocational school - find out what you need to do to get into the field AND get the knowledge to excel (for example, back to cars, good mechanics are constantly getting trained and getting SME certified to stay on top of their game).
In your off time, check your local community college - many of them have credit and non-credit courses you can take that are inexpensive. Some of them will lead to an associates degree that you can then take to a 4-year college for your bachelors (even if the credit class is in something you decide not to pursue - such as history - you now have those credits you can apply to your Associate Degree). Or look for short classes that are non-credit - let's say you are considering auto mechanic, my community college (and a lt of others) offer really inexpensive classes (just a few nights) in small-engine repair, You get two things out of this - you learn whether you want to fix engines for a living and, even if you don't, you can now fix your riding lawn mower (and your neighbor's :)).
Choosing what you want to do with your life is a process, and for most of us (I got lucky, I knew what I wanted to do in 8th/9th grade) it takes a while of experimentation to figure it out.