If you went through four years of school and are still not sure what you want to do you have a few choices - sit around and live with the parents, get a job and move on, declare a new major and take a few undergrad victory laps, or get into an advanced degree program. Let's explore these options a little more:
Sit around and live with the parents. You'll probably get a part-time job to get paid to support your social life, but the full-time job search will probably last for at least six months unless you are lucky. Companies that usually hire full-time college grads usually hire either right after the fall or spring semester, so you may have to wait until the next end of the semester to start actually working, but your interviews and offers will come before that time so you need to continually be looking.
With your time off and part-time job, you may have time to find out what others are saying about their employers and jobs which will help you make a good choice or avoid a bad decision like them. Also, your friends can refer you if you are someone that they would risk their office reputation on. Referral fees are much larger in corporations and large businesses, so you and your friend could split it if it works out.
Don't just sit around, though. Work a few part-time jobs and find yourself by using the experiences and time off to determine what you really enjoy compared to what you thought you enjoyed. We all have pictures of ourselves after college, and when you actually get there it may be better or worse than planned.
Get the first job and move on. Do what you are supposed to do after college - get a full-time job, buy some suits, and throw in the towel. What? That was a depressing thought, and it's really not that bad for those that research the companies in depth that they are considering. You may find out that the job is not right for you soon after, and then you move on to the next one hoping to get closer to what you like.
The important thing is to not lock yourself into an employment situation by racking up credit card debt or buying stuff that you can't really afford just because you have a bigger paycheck. Have a good time, but create a budget and save your money so that if your job is not working out your paycheck and financial situation is not holding you back from an opportunity that could make you much happier and benefit your career in the long run. This is the getting paid to figure it out method.
Declare a new major and take a few undergrad victory laps. It's never too late to decide that your major is not really for you. Hopefully you decide before senior year, but if not you should not force yourself to graduate unless it is financially not possible to take more courses. Most of your general education courses can be used to fulfill major requirements for 8-10 years depending where you go (maybe longer), so you wouldn't be starting over. I had a friend who switched majors after their junior year to a completely unrelated area of study, and they graduated in five years while working part-time and taking summer classes.
If you force yourself to graduate with a degree that you didn't really enjoy obtaining, chances are that your related job will not be very enjoyable. The key here is that if you don't enjoy your classes then you need to start taking new types of classes. I know that you want to be done with school, but it won't be worth it a year or two down the line when you're already unhappy with your job and area of work. That feeling will only grow and become more and more bottled up until you start taking it out on other people. Life's to short to be pissed for no reason, or for a reason that could have been prevented.
Get an advanced degree. If you enjoyed what you studied in undergrad, and don't feel ready for the full-time job go for a related advanced degree. The course work is more specialized, the projects and classmates will typically be more professional in nature, and many positions now require an advanced degree.
I only recommend this route if you enjoyed your undergrad courses, and you know that you do not want a full-time job yet. If you're unsure about which path to take between grad school and working, take your placement tests and interview with companies at the same time. The best way to learn is by doing, right? Grad school should not be a backup plan in case you don't get hired after your undergrad years, but it is for many students which ends up having mixed results.
