A lot depends on the Uni/College and the type of Course.
If you are looking to do a Degree at Art College they usually expect you to have done a Foundation year.
As a general rule, don't try to impress them - it's highly unlikely that you will succeed.
They normally look for potential - and to see if you have an eye for composition. They want to know what sort of person you are.
Best to take a range of things - and take all your contact sheets. It has been known for lecturers to seize on an image you have discarded and ask you why you didn't select it.
They should not be looking for technical ability - they will teach you that.
Just don't worry and be yourself.