The best way to get a grasp of what different subjects are about and what might appeal to you about them is to get hold of some Uni prospectuses (from your school Careers person or a big local library) and just sit and flick through them, looking at interesting sounding courses and what they involve. This is easier than on a website! They dont have to be Unis you might go to - any Uni will do at this stage. What subjects interest you? *Why*? Then look at similar courses at other Unis and see what is different, more/less interesting etc.
Dont forget to look at courses with unfamiliar titles - Development Studies, Social Anthropology, Environmental Studies, Social Policy etc, or 'area studies' like American Studies, Middle Eastern Studies etc that cover a wide breadth of study.
Go to some Open Days (again, any Uni). This will give you an idea of what 'being at Uni' might be like AND what makes University level different than A Levels. You can do this in Year 10 or Year 11 btw - it doesnt have to be the year you apply to Uni.