Hi,
Most of what everyone has said is good quality info and true as well

However I tend to come at this thing from a little bit of a different direction. To make this sort of decesion you need to have a goal in mind, a fixed outcome that you want to achieve with your life. Basically you want to design your life

That sounds riduculous but you will be doing it either intentionally or not. So if you want to be a specialist surgeon you have to do what they do to get to be a surgeon, a solicitor needs to be doing what solicitors need to be doing. If you want to run a successful business then why would you go through the training to be a doctor for example.
In my opinion far to many people just do the next thing that presents itself, in my case O levels, then BTEC Diploma, BTEC HNC, Degree (I got booted from that due to illness and disinterest), HND (Failed miserably again due to illness and disinterest), later did a part time BTEC Diploma and a BTEC HNC.
So I have spent years studying engineering (the early years) and then software engineering) all of which is and always was useless to me, I think I only ever managed to get one job based on the first Engineering HNC and that was a computer based job running a software system for a large company??
I wish I had thought about what I wanted to do and be when I was a kid and not just followed everyone else. I remember the decision that sent me down that road, my mate from school signed up for the BTEC course and I thought to my self 'OK I'll do that too'.
If I was doing it again I would probably take a much different route, something that would lead me to running my own business as I do now, just 20+ years faster.
If I was you I would talk to your parents, tell them that you want to defer your admission to uni so that you can get some sort of practical experience in the 'University of Life' and then work your behind off in a bunch of different situations.
I would also read as many self help books as you can over that time, starting with 'the 4 hour work week'. After a year if you have worked hard you will know what you want to do.
Just remember your parents only want you to be happy and successfull and society tells them that the best way to do that is to go to uni.
Good Luck
Jim